Rheem tankless water heater error codes
116 codes for RTGH-3, RTG-3, RTG-R-3, IKONIC, ThermaForce, Ruud Mid-Efficiency, each with the wording and page from Rheem's manuals.
All Rheem codes
Meanings are quoted from Rheem's manuals. The "Who" column is our reading of the manual's remedy: whether an owner can do the first checks, or the fix belongs to a licensed technician.
| Code | Manual meaning | Series | Who | Source |
|---|---|---|---|---|
| 1L | “Water heater has buildup of lime deposits.” The RTG-R-3 chart adds "Flushing the water heater is recommended." (RTG-R-3 manual, p. 74). The troubleshooting manual calls 1L a warning code, "Lime build-up detected in heat exchanger", and says the unit must be drained and flushed (AP21822 tech manual, p. 34). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 34; AP24838 tech manual p. 27; AP18000-2 manual p. 26 |
| P1 | “Not enough water flow to operate the unit.” What to check The RTG-R-3 chart adds "Water flow was low during recirculation cycle." and asks you to confirm there is no debris in the inlet water filter (RTG-R-3 manual, p. 74). The troubleshooting manual gives 0.4 GPM as the minimum flow to activate the heater (AP21822 tech manual, p. 34). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Owner can check | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 34; AP24838 tech manual p. 27; AP18000-2 manual p. 26 |
| 03 | “Manifold setting failure” Listed only in Rheem's troubleshooting manual for service professionals. Only for manifolded (multiple-unit) installations (AP21822 tech manual, p. 35). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 35; AP24838 tech manual p. 28 |
| 05 | “Low heat exchanger temperature detected” Listed only in Rheem's troubleshooting manuals for service professionals: 05 is a warning, and if the low temperature continues the heater shows error 28 (AP21822 tech manual, p. 35). Ruud Tankless Mid-Efficiency heaters use 05 for something else. Their chart reads "Air intake or vent exhaust opening may be blocked." (remedy: "Remove any blockage.") and "The vent pipes on the vent termination may not be connected properly." (remedy: contact a dealer or qualified service technician) (AP18000-2 manual, p. 26). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 35; AP24838 tech manual p. 28 |
| 07 | “Limited hot water condition” Listed only in Rheem's troubleshooting manual for service professionals. A warning shown only when a Wi-Fi controller is used, when the heater is set to water saving mode and controls the flow rate (AP21822 tech manual, p. 63). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 63; AP24838 tech manual p. 58 |
| 10 | “Incorrect inlet air volume” Listed only in Rheem's troubleshooting manual for service professionals. A warning: the heater ran before the vent was installed, or the blower is not creating enough ventilation (AP21822 tech manual, p. 37). The same manual names 10 a "hard lockout" whose reset starts with removing the front cover (AP21822 tech manual, p. 61). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 37; AP24838 tech manual p. 30 |
| 11 | “The gas shut-off valve is not fully opened.” What to check Troubleshooting manual name: "Flame Not Detected by Flame Rod". The heater attempts ignition 2 times before it shows 11 (AP21822 tech manual, p. 37). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Owner checks, then technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 37; AP24838 tech manual p. 30; AP18000-2 manual p. 26 |
| 12 | “Gas service has been interrupted.” What to check Second row in the same charts: "LP gas is running low (LP models only)." Troubleshooting manual name: "Detected Presence of Flame, Then Lost it", shown after the flame is lost 3 times in a row (AP21822 tech manual, p. 40). The EZ installation guides give "Check gas supply." as the first remedy, and the RTGH guide adds a DIP switch row (RTGH EZ guide, p. 7; RTG EZ guide, p. 2; RTG-R EZ guide, p. 2). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Owner checks, then technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 40; AP24838 tech manual p. 33; AP18000-2 manual p. 26 |
| 13 | “If this code is still displayed after taking the numbered steps above.” Only the Ruud Tankless Mid-Efficiency chart lists 13 (AP18000-2 manual, p. 26); the RTGH-3, RTG-3 and RTG-R-3 charts do not. Rheem's troubleshooting manuals name 13 only in the heading of a reset procedure for "hard lockouts" (10, 13 and 99) and have no section for it (AP21822 tech manual, p. 61; AP24838 tech manual, p. 56). | Ruud Mid-Efficiency | Technician | AP18000-2 manual p. 26; AP21822 tech manual p. 61; AP24838 tech manual p. 56 |
| 14 | “Water heater is overheating.” What to check The RTG-R-3 chart words it "Protective overheating wrap has been broken." (RTG-R-3 manual, p. 74). Troubleshooting manual name: "Over heat limiter is active"; the manual says this is normally caused by inadequate or wrong gas supply and/or venting (AP21822 tech manual, p. 41). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 41; AP24838 tech manual p. 34; AP18000-2 manual p. 26 |
| 15 | “Excessively hot water detected” Listed only in Rheem's troubleshooting manuals for service professionals: outlet or heat exchanger water above 207°F (97°C) for more than 15 seconds (AP21822 tech manual, p. 42). The Ruud Tankless Mid-Efficiency chart also lists 15, worded "The heat exchanger is too hot. Check for blockage in the vent.", with a call to a dealer or qualified service technician (AP18000-2 manual, p. 26). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 42; AP24838 tech manual p. 35 |
| 16 | “Outlet thermistor failure” Listed only in Rheem's troubleshooting manual for service professionals. Shown when the outlet water temperature is above the set point (AP21822 tech manual, p. 42). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 42; AP24838 tech manual p. 35 |
| 17 | “Leak sensor has detected water.” The meaning above is the RTG-R-3 chart's wording; the troubleshooting manuals head the code "Water leak detected" and say it is shown only when a Wi-Fi controller is used (AP21822 tech manual, p. 62; AP24838 tech manual, p. 57). Only the RTG-R-3 chart lists 17, with the remedy "There is a potential water leak. Contact a dealer or qualified service technician." (RTG-R-3 manual, p. 74). That manual's Leak Sensor section calls the alert "A017" (RTG-R-3 manual, p. 66). | RTGH-3, RTG-3, RTG-R-3 | Technician | RTG-R-3 manual p. 74; AP21822 tech manual p. 62; AP24838 tech manual p. 57 |
| 24 | “DIP switch malfunction” Listed only in Rheem's troubleshooting manual for service professionals. Shown when the UP/DOWN buttons on the built-in controller or remote are pressed for more than 20 seconds (AP21822 tech manual, p. 43). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 43; AP24838 tech manual p. 36 |
| 28 | “Low heat exchanger temperature detected” Listed only in Rheem's troubleshooting manual for service professionals. Follows warning 05 when the heat exchanger thermistor keeps detecting a low temperature (AP21822 tech manual, p. 35). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 35; AP24838 tech manual p. 28 |
| 29 | “Neutralizer is clogged.” What to check The chart row gives only "Contact a dealer or qualified service technician." (RTGH-3 manual, p. 75). We class 29 as mixed because the owner maintenance list in the same manual includes checking the condensate line for blockage and, if a neutralizer is installed, checking its medium once a year (RTGH-3 manual, p. 68). The RTGH EZ guide words the cause "Condensation Trap is clogged." (RTGH EZ guide, p. 7). Troubleshooting manual name: "Condensation not drained from collector": the electrode in the built-in drain trap reads the water level as full, or cannot read it (AP21822 tech manual, p. 43). The RTG-3 chart and the RTG-R-3 troubleshooting manual have no code 29, and AP21822 labels the water level electrode "FOR CONDENSING MODEL ONLY" (AP21822 tech manual, p. 19). | RTGH-3 | Owner checks, then technician | RTGH-3 manual p. 75; RTGH EZ guide p. 7; AP21822 tech manual p. 43 |
| 31 | “Faulty inlet thermistor.” | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 44; AP24838 tech manual p. 37; AP18000-2 manual p. 26 |
| 32 | “Heat exchanger thermistor malfunction” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 45; AP24838 tech manual p. 38 |
| 33 | “Faulty outlet thermistor.” | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 46; AP24838 tech manual p. 39; AP18000-2 manual p. 26 |
| 34 | “Ambient/air supply thermistor malfunction” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 47; AP24838 tech manual p. 40 |
| 35 | “Improper thermistor connection” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 48; AP24838 tech manual p. 41 |
| 48 | “Water leak detection disabled” Listed only in Rheem's troubleshooting manual for service professionals. Wi-Fi controller only: code 17 can be disabled through the Wi-Fi app for 24 hours, after which the heater shows warning 48 (AP21822 tech manual, p. 62). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 62; AP24838 tech manual p. 57 |
| 49 | “Water leak sensor not installed” Listed only in Rheem's troubleshooting manual for service professionals. Shown only when a Wi-Fi controller is used (AP21822 tech manual, p. 62). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 62; AP24838 tech manual p. 57 |
| 51 | “Main gas solenoid valve (SV) malfunction” Listed only in Rheem's troubleshooting manual for service professionals. The manual gives 51 and 52 the same explanation: the flame rod still detects flame a few seconds after the heater is turned off (AP21822 tech manual, pp. 49, 50). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 49; AP24838 tech manual p. 42 |
| 52 | “Proportional gas valve malfunction” Listed only in Rheem's troubleshooting manual for service professionals. Same explanation as 51 in that manual (AP21822 tech manual, pp. 49, 50). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 50; AP24838 tech manual p. 43 |
| 61 | “Faulty blower motor.” What to check Troubleshooting manual name: "Blower motor speed incorrect for combustion": the RPM signal is incorrect after the fan starts (AP21822 tech manual, p. 51). The Ruud Tankless Mid-Efficiency chart prints this row as "61 or 99" (AP18000-2 manual, p. 26). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 51; AP24838 tech manual p. 44; AP18000-2 manual p. 26 |
| 63 | “There is an abnormality in the pump's operation.” The chart's remedy starts with an owner step: "Remove any blockage that would prevent the pump from flowing water.", then "Contact a dealer or qualified service technician." (RTG-R-3 manual, p. 74). Troubleshooting manual name: "Recirculation pump speed incorrect" (AP24838 tech manual, p. 45). | RTG-R-3 | Owner checks, then technician | RTG-R-3 manual p. 74; AP24838 tech manual p. 45 |
| 65 | “Water motor failed” Listed only in Rheem's troubleshooting manual for service professionals; only the RTG-R-3 manual has a section for 65 (AP24838 tech manual, p. 46). AP21822 refers to a section 65 from codes 05 and 28 but has none (AP21822 tech manual, p. 35). The Ruud Tankless Mid-Efficiency chart also lists 65, worded "Faulty water flow solenoid.", with a call to a dealer or qualified service technician (AP18000-2 manual, p. 26). | RTG-R-3 | Technician | AP24838 tech manual p. 46 |
| 66 | “Faulty bypass motor.” The RTG-R-3 chart words it "Faulty water bypass motor" (RTG-R-3 manual, p. 74). | RTGH-3, RTG-3, RTG-R-3 | Technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 52; AP24838 tech manual p. 47 |
| 70 | “Microcomputer abnormality” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 53; AP24838 tech manual p. 48 |
| 71 | “Solenoid valve circuit failure.” Only the RTGH-3 chart lists 71. Its solution cell also says "Flushing procedure may need to be repeated for excessive lime and scale build-up.", the sentence the troubleshooting manual prints for 1L (RTGH-3 manual, p. 75; AP21822 tech manual, p. 34). The RTG-3 and RTG-R-3 charts do not list 71; both troubleshooting manuals do (AP21822 tech manual, p. 54; AP24838 tech manual, p. 49). | RTGH-3, RTG-3, RTG-R-3 | Technician | RTGH-3 manual p. 75; AP21822 tech manual p. 54; AP24838 tech manual p. 49 |
| 72 | “Flame rod detected flame before ignition” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 55; AP24838 tech manual p. 50 |
| 76 | “Built-in display (or remote controller) to water heater comm. failure” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 56; AP24838 tech manual p. 51 |
| 77 | “WiFi chip communication failure” Listed only in Rheem's troubleshooting manual for service professionals. A warning shown only when a Wi-Fi controller is used (AP21822 tech manual, p. 63). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 63; AP24838 tech manual p. 58 |
| 79 | “Blower motor current failure” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 58; AP24838 tech manual p. 53 |
| 80 | “Detected flame presence after closing solenoid valves” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 59; AP24838 tech manual p. 54 |
| 82 | “Installed chip error” Listed only in Rheem's troubleshooting manual for service professionals. | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 59; AP24838 tech manual p. 54 |
| 83 | “Configuration data restore failure” Listed only in Rheem's troubleshooting manual for service professionals. A warning shown only when a Wi-Fi controller is used (AP21822 tech manual, p. 63). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 63; AP24838 tech manual p. 58 |
| 84 | “Configuration write limit exceeded” Listed only in Rheem's troubleshooting manual for service professionals. A warning shown only when a Wi-Fi controller is used (AP21822 tech manual, p. 63). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 63; AP24838 tech manual p. 58 |
| 85 | “DIP switch not set for intended recirculation mode” Listed only in Rheem's troubleshooting manual for service professionals. A warning shown only with a Wi-Fi controller on heaters installed with a recirculation line, when the DIP switch on the control board and the Wi-Fi app settings do not match (AP21822 tech manual, p. 64). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 64; AP24838 tech manual p. 59 |
| 88 | “Reminder of flushing the heat exchanger and/or replacing the water treatment filter.” The reminder is off by default and can be set to 500, 750 or 1,000 hours of combustion (RTGH-3 manual, p. 76). The Use and Care manuals print a procedure to clear 88 after the maintenance is done (RTGH-3 manual, p. 77; RTG-3 manual, p. 79; RTG-R-3 manual, p. 76). The troubleshooting manual calls 88 a warning and says the unit will eventually shut down to protect itself (AP21822 tech manual, p. 60). | RTGH-3, RTG-3, RTG-R-3, Ruud Mid-Efficiency | Owner checks, then technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 60; AP24838 tech manual p. 55; AP18000-2 manual p. 26 |
| 89 | “High exhaust temperature detected” Listed only in Rheem's troubleshooting manual for service professionals. An over temperature limit switch on the secondary heat exchanger has tripped; the manual says this is normally caused by inadequate or wrong gas supply and/or venting (AP21822 tech manual, p. 61). | RTGH-3, RTG-3, RTG-R-3 | Technician | AP21822 tech manual p. 61; AP24838 tech manual p. 56 |
| 90 | “Air intake or vent exhaust opening may be blocked.” What to check The charts print one row for "90 or 99", with a second cause: "The vent pipes on the vent termination may not be connected properly." The troubleshooting manual says 90 occurs before the unit goes into ignition and 99 after it shuts down (AP21822 tech manual, p. 61). | RTGH-3, RTG-3, RTG-R-3 | Owner checks, then technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 61; AP24838 tech manual p. 56 |
| 99 | “Air intake or vent exhaust opening may be blocked.” What to check Same chart row as 90 ("90 or 99"). The troubleshooting manual says 99 occurs after the unit shuts down and lists it with 10 and 13 as a "hard lockout" whose reset starts with removing the front cover (AP21822 tech manual, p. 61). Ruud Tankless Mid-Efficiency heaters use 99 for something else: their chart prints "61 or 99" as "Faulty blower motor.", with a call to a dealer or qualified service technician (AP18000-2 manual, p. 26). | RTGH-3, RTG-3, RTG-R-3 | Owner checks, then technician | RTGH-3 manual p. 75; RTG-3 manual p. 77; RTG-R-3 manual p. 74; AP21822 tech manual p. 61; AP24838 tech manual p. 56 |
| 102-106 | “Manifolding communication error.” Manifolded installations only. The troubleshooting manual lists each code: 102 is "Manifolding comm. error between unit 2 and manager unit", and 103, 104, 105 and 106 are the same for units 3 to 6 (AP24838 tech manual, p. 59). The chart refers to the manual's Multiple Unit Controls section (RTG-R-3 manual, p. 74). | RTG-R-3 | Technician | RTG-R-3 manual p. 74; AP24838 tech manual p. 59 |
| 149 | “Water leak sensor not installed” Listed only in Rheem's troubleshooting manual for service professionals. Shown only when a Wi-Fi controller is used, if the leak sensor is missing or its connection to the display wire harness is lost (AP24838 tech manual, p. 59). | RTG-R-3 | Technician | AP24838 tech manual p. 59 |
| 176 | “Wifi display to water heater communication error.” The chart's remedy is "Confirm the cable connections are installed properly." (RTG-R-3 manual, p. 74). We class it as technician work because the same manual tells owners not to repair electrical wiring or the remote control (RTG-R-3 manual, p. 5). | RTG-R-3 | Technician | RTG-R-3 manual p. 74; AP24838 tech manual p. 60 |
| 195 | “The manager heater detects a failure in one of the manifolded heaters.” Manifolded installations only. The chart refers to the manual's Multiple Unit Controls section (RTG-R-3 manual, p. 74). | RTG-R-3 | Technician | RTG-R-3 manual p. 74; AP24838 tech manual p. 60 |
| 196 | “The manifolded unit detects incorrect local dip switch setting” Listed only in Rheem's troubleshooting manual for service professionals. Manifolded installations only (AP24838 tech manual, p. 60). | RTG-R-3 | Technician | AP24838 tech manual p. 60 |
| A01L | “Water heater has buildup of lime deposits.” The IKONIC service manual uses A018 for lime build-up (IKONIC service manual, p. 44). Neither document says that A01L and A018 are the same code. | IKONIC | Technician | IKONIC manual p. 107 |
| A011 | “The gas shut-off valve is not fully opened.” The IKONIC chart's remedy also asks you to check that venting and the air supply are not blocked (IKONIC manual, p. 107). Service manual name: "Flame Not Detected From Flame Rod", after 10 ignition attempts (IKONIC service manual, p. 38). | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC service manual p. 38 |
| A012 | “Gas service has been interrupted.” Second row: "LP gas is running low (LP models only)." Service manual name: "Unit Detected Flame and Lost It", after 15 flame losses in a row (IKONIC service manual, p. 41). | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC service manual p. 41 |
| A014 | “Water heater is overheating.” Service manual name: "Over Heat Limiter (OHL) activated"; the heater has an Over Heat Limiter and an Over Heat Limit Fuse (IKONIC service manual, p. 43). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 43 |
| A017 | “Leak sensor has detected water.” The chart points to the manual's Leak Sensor section: if water is found outside the heater, contact a dealer or qualified service technician immediately; if no leak is found, a 24-hour override is available in the SETTINGS menu (IKONIC manual, p. 103). The IKONIC service manual does not list A017. | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC manual p. 103 |
| A018 | “Lime build-up inside the heat exchanger” Listed only in Rheem's IKONIC service manual for service professionals. The IKONIC Use and Care chart shows lime build-up as A01L (IKONIC manual, p. 107). | IKONIC | Technician | IKONIC service manual p. 44 |
| A029 | “Blocked condensate line.” Service manual name: "Condensate blockage" (IKONIC service manual, p. 45). The IKONIC manual asks owners to inspect the condensate drain line on a regular basis (IKONIC manual, p. 94). | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC service manual p. 45 |
| A031 | “Faulty inlet water thermistor.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 46 |
| A032 | “Faulty heat exchanger thermistor.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 47 |
| A033 | “Faulty outlet water thermistor.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 48 |
| A035 | “Improper thermistor connection.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 49 |
| A036 | “Faulty exhaust thermistor.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 50 |
| A055 | “Faulty gas valve.” Service manual name: "Gas motor failed", the motor that positions the butterfly valve in the venturi (IKONIC service manual, p. 51). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 51 |
| A061 | “Faulty blower motor.” | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 52 |
| A063 | “(Built-in recirculation) pump abnormality.” SR models only (IKONIC manual, p. 107). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 53 |
| A065 | “Faulty water flow solenoid.” Service manual name: "Water volume control valve malfunction" (IKONIC service manual, p. 54). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 54 |
| A066 | “Faulty bypass solenoid.” Service manual name: "Water bypass control valve malfunction" (IKONIC service manual, p. 55). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 55 |
| A070 | “Faulty control board.” Service manual name: "Microcomputer Abnormality" (IKONIC service manual, p. 56). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 56 |
| A071 | “Faulty gas solenoid valve.” Service manual name: "Gas Air ratio valve malfunction": the flame rod detects flame for 8 seconds after the heater is turned off (IKONIC service manual, p. 57). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 57 |
| A072 | “Flame detected before ignition.” Service manual name: "Flame rod malfunction" (IKONIC service manual, p. 58). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 58 |
| A082 | “Software error.” Service manual name: "Installed Chip Error", a problem with the gas chip on the control board (IKONIC service manual, p. 59). | IKONIC | Technician | IKONIC manual p. 107; IKONIC service manual p. 59 |
| A090 | “Air intake or vent exhaust opening may be blocked.” Two more rows in the IKONIC chart: "The vent pipes on the vent termination may not be connected properly." and "Blocked vent termination or inlet air filter.", both with "Contact a dealer or qualified service technician." (IKONIC manual, p. 107). | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC service manual p. 60 |
| A200 | “Water Heater Communication Failure.” Listed only in Rheem's IKONIC service manual for service professionals: the user interface is not communicating with the control board (IKONIC service manual, p. 61). | IKONIC | Technician | IKONIC service manual p. 61 |
| A2## | “WATER HEATER COMM. FAILURE INSTANCE ## (## IS NO.02 TO NO,20)” Listed only in Rheem's IKONIC service manual for service professionals. In a manifold of up to 20 heaters, the manager heater shows A2## when another heater has an error, where ## is that heater's instance number; the manual's example is A205 (IKONIC service manual, p. 62). Quoted as printed. | IKONIC | Technician | IKONIC service manual p. 62 |
| T110 | “WiFi chip communication error” Listed only in Rheem's IKONIC service manual for service professionals. | IKONIC | Technician | IKONIC service manual p. 63 |
| T111 | “Reminder of flushing the heat exchanger and/or replacing the water tratment filter” Quoted as printed ("tratment"). The service alert can be set to 500, 750 or 1000 hours; the Use and Care manual gives the factory setting as OFF (IKONIC manual, p. 76), the service manual as 500 hours (IKONIC service manual, p. 35). The service manual calls T111 a warning after which the unit will eventually shut down (IKONIC service manual, p. 64). Alarms are cleared from the SERVICE menu (IKONIC manual, p. 106). | IKONIC | Owner checks, then technician | IKONIC manual p. 107; IKONIC service manual p. 64 |
| T113 | “Not enough hot water to operate the unit.” The chart's remedy is printed "Increase the water flow from the fuxtures." (IKONIC manual, p. 107). The service manual says the flow rate is less than 0.4 GPM and the heater will not activate (IKONIC service manual, p. 65). | IKONIC | Owner can check | IKONIC manual p. 107; IKONIC service manual p. 65 |
| T115 | “Pump schedule disable - No time received.” Listed only in Rheem's IKONIC service manual for service professionals. Applies to heaters installed with a recirculation line and a pump schedule; the manual says to recheck the scheduled time in the EcoNet app (IKONIC service manual, p. 66). | IKONIC | Technician | IKONIC service manual p. 66 |
| T116 | “Manifold unit fault.” Listed only in Rheem's IKONIC service manual for service professionals. Manifolded installations only (IKONIC service manual, p. 66). | IKONIC | Technician | IKONIC service manual p. 66 |
| F000 | “Heat exchanger temperature sensor fault.” | ThermaForce | Technician | I&O manual 84160404 p. 5-5; Controller manual 84162404 p. 1-40 |
| F002 | “High heat exchanger temperature during DHW demand.” | ThermaForce | Technician | I&O manual 84160404 p. 5-5; Controller manual 84162404 p. 1-40 |
| F003 | “High flue temperature.” | ThermaForce | Technician | I&O manual 84160404 p. 5-5; Controller manual 84162404 p. 1-40 |
| F004 | “No flame detected during four ignition trials.” The installation manual's list starts with verifying that the external gas shutoff valve is open, then moves to gas inlet pressure, the condensate drain, venting, grounding, the ignitor and replacement of parts (I&O manual 84160404, p. 5-5). | ThermaForce | Technician | I&O manual 84160404 p. 5-5; Controller manual 84162404 p. 1-40 |
| F005 | “No flame detected during operation.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F006 | “Flame detected when burner is off.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F007 | “Low flame signal.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F008 | “Incorrect fan speed” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F009 | “Control module internal fault.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F010 | “Heat exchanger temperature sensor open.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F011 | “Heat exchanger temperature sensor short.” Listed in the installation manual (I&O manual 84160404, p. 5-6); the table in Controller manual 84162404 does not include F011. | ThermaForce | Technician | I&O manual 84160404 p. 5-6 |
| F012 | “Flue temperature sensor open.” | ThermaForce | Technician | I&O manual 84160404 p. 5-6; Controller manual 84162404 p. 1-41 |
| F013 | “DHW inlet temperature sensor open/short” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-41 |
| F014 | “Heat exchanger temperature sensor mounting fault.” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-41 |
| F015 | “High cabinet temperature” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-41 |
| F016 | “DHW outlet temperature sensor mounting fault” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-41 |
| F017 | “DHW bypass valve fault” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42 |
| F018 | “Flue/Combustion Air blockage.” The user's manual does not name F018, but says that if a vent blockage is easily accessible and removable, remove it and reset the unit by touching the wrench for 2 seconds; if it is not, contact a qualified service agency (User's manual 84161404, p. 4). | ThermaForce | Owner checks, then technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42; User's manual 84161404 p. 4 |
| F019 | “Boiler Memory Module (BMM) fault.” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42 |
| F021 | “Critical parameter changed” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42 |
| F028 | “Reset button fault” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42 |
| F029 | “Gas valve fault.” | ThermaForce | Technician | I&O manual 84160404 p. 5-7; Controller manual 84162404 p. 1-42 |
| F040 | “Cabinet temperature sensor open.” | ThermaForce | Technician | I&O manual 84160404 p. 5-8; Controller manual 84162404 p. 1-42 |
| F041 | “Cabinet temperature sensor short” | ThermaForce | Technician | I&O manual 84160404 p. 5-8; Controller manual 84162404 p. 1-42 |
| F042 | “Cascade DHW not available” | ThermaForce | Technician | I&O manual 84160404 p. 5-8; Controller manual 84162404 p. 1-42 |
| -- (Blinking) | “Water presssure sensor fault” Printed without a number, as two blinking dashes. Quoted as printed ("presssure"). | ThermaForce | Technician | I&O manual 84160404 p. 5-8; Controller manual 84162404 p. 1-43 |
| n030 | “DHW outlet temperature sensor open/short” | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n040 | “Cascade communication lost” | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n041 | “Cascade system sensor open” | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n120 | “Maintenance recommended” Based on hours of use (I&O manual 84160404, p. 5-9). The user's manual says annual maintenance must only be done by a qualified service technician (User's manual 84161404, p. 12). | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n121 | “Maintenance required, limited DHW output” Hot water output stays limited until maintenance is performed (I&O manual 84160404, p. 5-9). | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n122 | “Maintenance required, no DHW output” Hot water output is disabled until maintenance is performed (I&O manual 84160404, p. 5-9). | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n150 | “High heat exchanger temperature, limited output” | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-44 |
| n151 | “High flue temperature, limited output” | ThermaForce | Technician | I&O manual 84160404 p. 5-9; Controller manual 84162404 p. 1-45 |
| n152 | “Flue temperature sensor mounting fault” | ThermaForce | Technician | I&O manual 84160404 p. 5-10; Controller manual 84162404 p. 1-45 |
| n201 | “Heat exchanger air purge function activated” | ThermaForce | Technician | I&O manual 84160404 p. 5-10; Controller manual 84162404 p. 1-45 |
| n202 | “High flue temperature, burner disabled” | ThermaForce | Technician | I&O manual 84160404 p. 5-10; Controller manual 84162404 p. 1-45 |
| n245 | “Flue gas back flow, fan on low speed” | ThermaForce | Technician | I&O manual 84160404 p. 5-10; Controller manual 84162404 p. 1-45 |
How to read a Rheem code
On RTGH-3, RTG-3 and RTG-R-3 heaters the code appears in the LED display of the remote control RTGH-3 Use and Care Manual, p. 74. Condensing and non-condensing indoor models also show it on a built-in controller RTGH-3 and RTG-3 Troubleshooting Manual, AP21822, p. 21. Most codes are two digits; 1L and P1 include a letter.
The Service Error Code Chart in each Use and Care manual lists only some of the codes RTGH-3 manual, p. 75; RTG-3 Use and Care Manual, p. 77; RTG-R-3 Use and Care Manual, p. 74. The rest come from Rheem’s troubleshooting manuals, written for technicians and service professionals only AP21822 tech manual, p. 7.
IKONIC heaters show codes such as A011 or T111 on the LCD of the user interface IKONIC Use and Care Manual, pp. 106–107. On ThermaForce heaters (RTGH-L199i; both names are from rheem.com, not the manuals), fault codes such as F004 flash on the main display I&O manual 84160404, p. 5-5.
Clearing a code
The RTGH-3, RTG-3 and RTG-R-3 manuals print the same sequence RTGH-3 manual, p. 74; RTG-3 manual, p. 76; RTG-R-3 manual, p. 73:
- Close all hot water taps. Turn the heater off with POWER ON/OFF on the remote, wait about 5 minutes, turn it on and open a hot tap.
- If the code remains, turn the heater off, unplug it for about 30 seconds, plug it back in, follow the chart for that code and restart.
- If the code is still shown, turn the heater off, write the code down and call for service. If the code is not in the chart, turn the heater off immediately and call.
The troubleshooting manual calls 10, 13 and 99 “hard lockouts” and resets them with the front cover off AP21822 tech manual, p. 61. Only a qualified service technician should remove that cover RTGH-3 manual, p. 49.
IKONIC heaters clear codes from the SERVICE menu with “Clear Alarms?” IKONIC Use and Care Manual, p. 106. For ThermaForce, the installation manual resets fault codes by touching the wrench for 2 seconds after the cause is resolved I&O manual 84160404, p. 5-5. The user’s manual gives owners that reset only for a blocked vent that is easily accessible and removable; otherwise it says to contact a qualified service agency User’s manual 84161404, p. 4.
When to stop and call a professional
If you smell gas, follow the block on the manual’s cover; its last step is not to return home until the gas supplier or fire department authorizes it RTGH-3 manual, p. 1. Do not try to find a gas leak yourself RTGH-3 manual, p. 5.
Owners should not repair electrical wiring, gas piping, the remote control, burners, vent connectors or other safety devices RTGH-3 manual, p. 5, or disassemble the heater RTGH-3 manual, p. 8. Turn off the manual gas shut-off valve if the heater has been through overheating, fire, flood or physical damage, or if the gas does not shut off RTGH-3 manual, p. 5.
Hard-wiring is for a qualified electrician RTGH-3 manual, p. 47. The RTGH-3 (Rev 06), RTG-3 (Rev 06), RTG-R-3 and IKONIC manuals recommend not connecting the heater to a GFCI or AFCI circuit RTGH-3 manual, p. 47; RTG-3 manual, p. 44; RTG-R-3 manual, p. 44; IKONIC Use and Care Manual, p. 69. The Rev 04 manuals for ECOH-3 and ECO-3 models, the RTGH Easy Installation Guide and the Ruud AP18000-2 manual say not to ECOH-3 Use and Care Manual, p. 47; ECO-3 Use and Care Manual, p. 44; RTGH EZ guide, p. 5; AP18000-2 manual, p. 55.
Questions, adjustments and repairs go to your installer, plumbing contractor or licensed service agent. If the problem is still not solved, Rheem lists its Manufacturer National Service Department at 1-866-720-2076 RTGH-3 manual, p. 75.
Rheem is a trademark of its owner. How House Works is not affiliated with or endorsed by Rheem.
Sources
- Rheem Manufacturing Company. RTGH-3 Use and Care Manual. AP21820 Rev 06, no printed date; cover title: Super High Efficiency Condensing Tankless Water Heater Use and Care Manual; the same file is posted for Ruud RUTGH models; p. 1 is the unnumbered cover. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. ECOH-3 Use and Care Manual. AP21820 Rev 04, no printed date; cover title: Super High Efficiency Condensing Tankless Water Heater Use and Care Manual; Rev 04 of the RTGH-3 manual, linked from the ECOH-3 product page. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTG-3 Use and Care Manual. AP22009 Rev 06, no printed date; cover title: High-Efficiency Non-Condensing Tankless Water Heater Use and Care Manual; the same file is posted for Ruud RUTG models. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. ECO-3 Use and Care Manual. AP22009 Rev 04, no printed date; cover title: High-Efficiency Non-Condensing Tankless Water Heater Use and Care Manual; Rev 04 of the RTG-3 manual, linked from the ECO-3 product pages. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTG-R-3 Use and Care Manual. AP23962 Rev 02, no printed date; cover title: High-Efficiency Non-Condensing Tankless Water Heater with Recirculation Use and Care Manual; the same file is posted for Ruud RUTG-R models. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTGH Tankless Easy Installation Guide. AP23365, no revision or date printed; no page numbers printed, pages given are PDF pages. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTG Tankless Easy Installation Guide. AP23366, no revision or date printed; no page numbers printed, p. 2 is the PDF page. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTG-R Tankless Easy Installation Guide. AP23964 Rev 00, print-file stamp 7/7/25; no page numbers printed, p. 2 is the PDF page. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTGH-3 and RTG-3 Troubleshooting Manual. AP21822 Rev 02, no issue date printed; cover title: High and Super High Efficiency Tankless Water Heater Troubleshooting Manual; written for technicians and service professionals only (p. 7). Accessed Oct 12, 2026.
- Rheem Manufacturing Company. RTG-R-3 Troubleshooting Manual. AP24838 Rev 01, no issue date printed; cover title: High Efficiency Tankless Water Heater with Recirculation Troubleshooting Manual; written for technicians and service professionals only (p. 6). Accessed Oct 12, 2026.
- Rheem Manufacturing Company. IKONIC Use and Care Manual. AP22745 Rev 07, no printed date; cover title: Condensing Tankless Water Heater Use and Care Manual; Ruud's S and SR Series pages post Rev 06. Accessed Oct 12, 2026.
- Rheem Manufacturing Company. IKONIC Technical Training and Service Manual. AP23209 Rev 03, no printed date; written for technicians and service professionals only (p. 4). Accessed Oct 12, 2026.
- Rheem Sales Co. / IBC Technologies. User's Information Manual 84161404. Document 84161404, May 2023; cover title: User's Information Manual, High Efficiency Condensing Tankless Water Heater, 199,000 Btu/hr Model (Natural Gas or Propane); the manual does not print the names ThermaForce, RTGH-L199i or L-Series, which come from the rheem.com and ruud.com product pages that post it (2026-10-12). Accessed Oct 12, 2026.
- Rheem Sales Co. / IBC Technologies. Installation and Operating Instructions 84160404. Document 84160404, May 2023; cover title: Installation and Operating Instructions, High Efficiency Condensing Tankless Water Heater; page numbers are printed by section (p. 5-5 is PDF page 67); the manual does not print the names ThermaForce, RTGH-L199i or L-Series, which come from the rheem.com and ruud.com product pages that post it (2026-10-12). Accessed Oct 12, 2026.
- Rheem Sales Co. / IBC Technologies. Controller Manual 84162404. Document 84162404, May 2023; cover title: Controller Manual, Tankless Water Heater Controller; page numbers are printed by section (p. 1-40 is PDF page 44); the manual does not print the names ThermaForce, RTGH-L199i or L-Series, which come from the rheem.com and ruud.com product pages that post it (2026-10-12). Accessed Oct 12, 2026.
- Rheem Manufacturing Company (posted on ruud.com). Tankless Water Heater Use and Care Manual AP18000-2. AP18000-2 Rev 03, no printed date; cover title: Tankless Water Heater Use and Care Manual, Noncondensing 199,900 Btu/h, 180,000 Btu/h, and 150,000 Btu/h Models; the manual prints no model numbers and no -3 suffix; ruud.com posts it on its Tankless Mid-Efficiency 70, 84 and 95 product pages (2026-10-12). Accessed Oct 12, 2026.