Rheem, Ruud, Richmond gas water heater status light codes

Rheem water heater status light off: control off or pilot out

Checked October 2026

Short answer On Rheem, Ruud and Richmond status light models, a dark light means the gas control is off, the pilot is out, or millivoltage is too low. Turn the control on or relight the pilot by the label; thermopile checks are technician work. See what to check

What it means

Rheem’s table gives a dark status light three possible conditions, in this order: “Combination Gas Control turned off”, “Pilot not lit” and “Insufficient power supply (millivoltage)” (AP23060 Rev 01, p. 24). The label legend sums them up as “Control Off/Pilot Out”. The Ultra Low NOx manuals word the first one “Combination Gas Control (Thermostat) turned off.” (AP23699, p. 24).

The light also goes dark on purpose. When you turn the knob to OFF, the STATUS light “will briefly stay lit, then go off after a short period of time” (AP23060 Rev 01, p. 17). And when you light the pilot, you hold the knob in until the STATUS light begins to blink (AP23060 Rev 01, p. 17). With the knob at OFF, a dark light is what the label describes.

The NOTICE above the table sets the order: “If pilot is not lit and the status light is not blinking or constantly on, follow the lighting instructions”, then read the code once the light blinks (AP23060 Rev 01, p. 24).

Check these first

In the table’s order, with the steps from the lighting label in the same manual:

1. Smell for gas before lighting: all around the heater and next to the floor, because some gas is heavier than air (AP23060 Rev 01, p. 17). If you smell gas, stop and follow the steps at the top of this page.
2. If the knob is at OFF, the table’s fix is to follow the operating instructions to turn the gas control on (AP23060 Rev 01, p. 24). In this manual the operating instructions start with the lighting label (AP23060 Rev 01, pp. 2, 17).
3. Light the pilot by the label. Turn the knob to OFF and wait five minutes; remove the outer door, but not the inner door; turn the knob to PILOT; hold it all the way in and press the piezo button several times until the STATUS light begins to blink; check the pilot flame through the sight glass (AP23060 Rev 01, p. 17).
4. If the STATUS light has not started blinking after 90 seconds and the pilot is not lit, the label says to repeat steps 2 through 6. If the pilot will not stay lit after several attempts, turn the knob to OFF and call your service technician or gas supplier (AP23060 Rev 01, p. 17).
5. The label’s last steps are to replace the outer door, release the knob (it should pop back out) and set the knob to the temperature you want. If the knob does not pop back out, stop and immediately call your service technician or gas supplier (AP23060 Rev 01, p. 17).
6. If the pilot lights but goes out when you let go of the knob, the NOTICE says to repeat the lighting instructions and keep the knob depressed until the pilot is lit and the code can be fully read (AP23060 Rev 01, p. 24). Two red blinks, for example, mean low thermopile voltage; see 2 blinks.

When to call a licensed technician

• Low millivoltage. The table’s checks for it are the thermopile connector at the gas control, the thermopile wires (replaced if damaged) and the pilot assembly (AP23060 Rev 01, p. 24). Rheem’s chart also lists a disconnected thermopile as the first cause of a pilot that goes out when the knob is released and says to make sure the connectors at the gas control are connected properly (AP23060 Rev 01, p. 22). We list this work for a technician because it is on the gas control and the pilot. The table calls this condition “Insufficient power supply (millivoltage)”.
• A pilot that will not stay lit. The chart’s other causes are a defective thermopile, a defective safety magnet, an opened single use gas shut-off device in the gas control, and a tripped combustion shutoff device. Each goes to a qualified service technician, and the two gas control causes mean replacing the gas control (AP23060 Rev 01, p. 22).
• A pilot that will not light. The chart names air in the gas line, a clogged pilot orifice and a pinched or clogged pilot tube, all for a qualified service technician (AP23060 Rev 01, p. 22).

The manual’s CAUTION on the same page says not to attempt repair of gas piping, the gas control, burners, vent connectors or other safety devices (AP23060 Rev 01, p. 22).

Related codes: Status light steady, 1 blink, 2 blinks. All Rheem gas tank water heaters codes

Rheem water heater status light stays on: pilot recently out or knob just turned off

Checked October 2026

Short answer On Rheem, Ruud and Richmond status light models, a light that stays on without blinking means the pilot recently went out and the thermopile is cooling down, or the knob was just turned to OFF. Rheem's fix is to light the pilot by the label. See what to check

What it means

Rheem’s table calls this state “Constantly lit” and gives it two causes: the pilot recently went out and the thermopile is cooling down, or the temperature knob was recently turned to OFF (AP23060 Rev 01, p. 24). The light does not blink, so it is not a count.

The table prints no color for this row (AP23060 Rev 01, p. 24). The note under the label legend says that when the knob is turned to OFF with the pilot lit, the status light “will briefly stay lit and turn from blue to red” (AP23060 Rev 01, p. 24), and the lighting label says it will “briefly stay lit, then go off after a short period of time” (AP23060 Rev 01, p. 17). A steady light right after you turned the knob to OFF is that sequence. “Solid red” is not printed as a code in any of the current Rheem manuals collected for this site.

Check these first

The table’s remedy is the same for both causes: “Follow the lighting instructions as detailed on the water heater and it’s Use & Care manual to light the pilot” (AP23060 Rev 01, p. 24).

1. If you smell gas, stop and follow the steps at the top of this page. The label says to smell all around the heater and next to the floor before lighting (AP23060 Rev 01, p. 17).
2. If you turned the knob to OFF yourself, the light staying on for a short time and then going off is what the label describes (AP23060 Rev 01, p. 17).
3. If the pilot went out, light it by the label. It starts with the knob at OFF and a five-minute wait to clear out any gas; then the knob goes to PILOT and you hold it in while pressing the piezo button until the STATUS light begins to blink (AP23060 Rev 01, p. 17).
4. If the pilot lights but goes out when you release the knob, repeat the lighting instructions and keep the knob depressed until the code can be fully read, as the NOTICE says (AP23060 Rev 01, p. 24). The code then tells you more; low thermopile voltage, for example, is 2 blinks.
5. If the pilot will not stay lit after several attempts, turn the knob to OFF and call your service technician or gas supplier (AP23060 Rev 01, p. 17).

When to call a licensed technician

• A pilot that keeps going out. Rheem’s chart lists a disconnected thermopile (make sure its connectors at the gas control are connected properly), a defective thermopile, a defective safety magnet, an opened single use gas shut-off device in the gas control and a tripped combustion shutoff device. The chart names a qualified service technician for all but the first; we list the first for a technician too, because the connectors are on the gas control (AP23060 Rev 01, p. 22).
• A pilot that is lit while the light stays on without blinking. The table has no row for that and gives the owner no step; the manual’s “If you need service” page lists who to call (AP23060 Rev 01, p. 28).
• Any repair of the gas control, burners or other safety devices, which the CAUTION on the troubleshooting page refers to qualified service personnel (AP23060 Rev 01, p. 22).

Related codes: Status light off, 1 blink, 2 blinks. All Rheem gas tank water heaters codes

Rheem water heater 2 blinks: low thermopile voltage

Checked October 2026

Short answer On Rheem, Ruud and Richmond status light models, two red blinks every three seconds mean low thermopile voltage with the pilot lit. The table's fixes at the thermopile and pilot are technician work. Power vent and powered damper LEDs use two flashes differently. See what to check

What it means

Two red blinks every three seconds is the label’s “Thermopile Voltage Low”. The table under it is more exact: “Low thermopile voltage however pilot is lit” (AP23060 Rev 01, p. 24). The pilot is burning, but the thermopile voltage is low.

The same table has a second thermopile row. “Insufficient power supply (millivoltage)” is one of the causes of a light that is off, and its checks are the same three as for two blinks: the thermopile connector at the gas control, the thermopile wires, and the pilot assembly (AP23060 Rev 01, p. 24). That case has its own page: status light off.

Check these first

The table gives this row no step that stops short of the thermopile and the pilot, so the owner’s part is short:

1. If you smell gas, stop and follow the steps at the top of this page.
2. Read the code with the pilot lit: two red blinks every three seconds (AP23060 Rev 01, p. 24). AP17110-1 (01/15) prints no colors, so on that manual count the blinks only (AP17110-1, p. 24).
3. If the pilot goes out and will not stay lit after several attempts at the lighting label, turn the knob to OFF and call your service technician or gas supplier (AP23060 Rev 01, p. 17).
4. Have the model and serial number from the rating plate ready, and call your installer, plumbing contractor or service agency first; the manual lists Rheem’s Manufacturer’s National Service Department at 1-866-279-4566 as the next step (AP23060 Rev 01, p. 28).

When to call a licensed technician

• The table’s three checks: “Check thermopile connector to the Combination Gas Control to ensure it is properly connected”, check the thermopile wires for damage and replace them if needed, and inspect the pilot assembly (AP23060 Rev 01, p. 24). We list these for a technician: the connector is on the gas control, and the CAUTION on the troubleshooting page refers repairs of the gas control, burners and other safety devices to qualified service personnel (AP23060 Rev 01, p. 22).
• A defective thermopile. Rheem’s chart says it “should be replaced by a qualified service technician” (AP23060 Rev 01, p. 22).

The status light manuals give no millivolt value for this code, so this page gives none.

Related codes: Status light off, Status light steady, 8 blinks. All Rheem gas tank water heaters codes

Rheem water heater 5 blinks: water temperature sensor failure

Checked October 2026

Short answer On Rheem, Ruud and Richmond status light models, five red blinks every three seconds mean water temperature sensor failure; Rheem's only step is to contact a qualified service technician. On power vent and powered damper LEDs, five flashes mean something else. See what to check

What it means

Five red blinks every three seconds is the label’s “Temperature Sensor Failure”. The table under it says “Water temperature sensor failure”, and its remedy is “Contact a qualified service technician. See “IF YOU NEED SERVICE” on page 28” (AP23060 Rev 01, p. 24). The Ultra Low NOx manuals print the same row (AP23699, p. 24; AP22858, p. 23).

The status light manuals say nothing more about this sensor: not where it is, and not what the control does while the code shows.

Check these first

The manual gives the owner one step for five blinks: contact a qualified service technician (AP23060 Rev 01, p. 24).

1. If you smell gas, stop and follow the steps at the top of this page.
2. Read the code with the pilot lit, as the NOTICE above the table says, and count the red blinks in one three-second cycle (AP23060 Rev 01, p. 24).
3. Have the model and serial number from the rating plate ready. Call your installer, plumbing contractor or service agency first; the manual lists Rheem’s Manufacturer’s National Service Department at 1-866-279-4566 as the next step (AP23060 Rev 01, p. 28).

When to call a licensed technician

• For the code itself. Every status light manual gives five blinks the same remedy (AP23060 Rev 01, p. 24; AP19928 Rev 02, p. 24).
• For any work on the gas control or its sensors. The manual’s CAUTION refers repairs of the gas control and other safety devices to qualified service personnel (AP23060 Rev 01, p. 22), and replacing a defective gas control is a job for a qualified service technician (AP23060 Rev 01, p. 23).

Related codes: 8-2 flashes, ● ○ ● ● ○ ●, A022. All Rheem gas tank water heaters codes

Rheem water heater 8 blinks: false pilot flame signal

Checked October 2026

Short answer On Rheem, Ruud and Richmond status light models, eight red blinks every three seconds mean a false pilot flame signal (Flame Sense Error); Rheem's only step is to contact a qualified service technician. Gas valve LED tables have no plain eight-flash code. See what to check

What it means

Eight red blinks every three seconds is the label’s “Flame Sense Error”. The table under it says “False pilot flame signal”, and its remedy is “Contact a qualified service technician. See “IF YOU NEED SERVICE” on page 28” (AP23060 Rev 01, p. 24). The Ultra Low NOx manuals print the same row (AP23699, p. 24; AP22858, p. 23).

The status light manuals give no cause and no check beyond the row.

Check these first

The manual gives the owner one step for eight blinks: contact a qualified service technician (AP23060 Rev 01, p. 24).

1. If you smell gas, stop and follow the steps at the top of this page.
2. Read the code with the pilot lit, as the NOTICE above the table says (AP23060 Rev 01, p. 24).
3. Have the model and serial number from the rating plate ready. Call your installer, plumbing contractor or service agency first; the manual lists Rheem’s Manufacturer’s National Service Department at 1-866-279-4566 as the next step (AP23060 Rev 01, p. 28).

When to call a licensed technician

• For the code itself, in every status light manual (AP23060 Rev 01, p. 24; AP20849 Rev 02, p. 24).
• For any work on the pilot, the burner or the gas control. Cleaning the burner “must be performed only by qualified service personnel”, and the burner chamber is a sealed area whose access door gasket must be replaced if the door is removed (AP23060 Rev 01, p. 21). The troubleshooting CAUTION refers repairs of the gas control and other safety devices to qualified service personnel (AP23060 Rev 01, p. 22).

Related codes: 6-4 flashes, 5 flashes, A028. All Rheem gas tank water heaters codes

Rheem water heater 9 blinks: chamber sensor failure (Ultra Low NOx)

Checked October 2026

Short answer Nine red blinks mean chamber sensor failure on models covered by five Ultra Low NOx status light manuals (two add "or bimetal switch activated"). Rheem's only step is to contact a qualified service technician. Other status light manuals do not list nine blinks. See what to check

What it means

Nine red blinks every three seconds is the label’s “Chamber Sensor Failure”. Only the Ultra Low NOx status light manuals print it, in two wordings, and both rows say “Contact a qualified service technician. See “IF YOU NEED SERVICE” on page 28”:

• “Chamber sensor failure.” in AP23698, AP23699 and AP22858, the manuals for the Ultra Low NOx Skinny models, the Performance Ultra Low NOx line and the Ultra Low NOx High BTU models (AP23699, p. 24; AP22858, p. 23).
• “Chamber sensor failure or bimetal switch activated.” in AP20849 Rev 02 and AP19928 Rev 02, the manuals for the High Demand Ultra Low NOx Atmospheric and the Heavy Duty Ultra Low NOx models (AP20849 Rev 02, p. 24; AP19928 Rev 02, p. 24).

The status light manuals AP23060 Rev 01, AP16801-2 (08/14) and AP17110-1 (01/15) have no nine-blink row, so for the Performance and Performance Plus Atmospheric and the other heaters covered by them, Rheem does not describe nine blinks (AP23060 Rev 01, p. 24).

The same five Ultra Low NOx manuals add ten blinks, “Chamber temperature shutdown.”, with the same remedy (AP23699, p. 24). None of them says where the chamber sensor is or what it measures.

Check these first

The table gives the owner one step for nine blinks: contact a qualified service technician (AP23699, p. 24).

1. If you smell gas, stop and follow the steps at the top of this page.
2. Check which manual your heater has. Its AP number is on the cover, and the product pages on rheem.com, ruud.com and richmondwaterheaters.com link each model line to its manual. If your manual has no nine-blink row, this code is not defined for your heater.
3. Read the code with the pilot lit. The NOTICE above the table in AP23698, AP23699 and AP22858 says the pilot burner must be lit to view status light codes (AP23699, p. 24).
4. Have the model and serial number from the rating plate ready. Call your installer, plumbing contractor or service agency first; the manual lists Rheem’s Manufacturer’s National Service Department at 1-866-279-4566 as the next step (AP23699, p. 28).

When to call a licensed technician

• For the code itself, in all five manuals that print it (AP23699, p. 24; AP19928 Rev 02, p. 24).
• For any work behind the burner access door. The installation section of AP23699 says the burner chamber is designed to be sealed with a gasket and tamper resistant screws, that the burner access door should not be removed unless absolutely necessary and only by a qualified service technician, and that a new gasket must go on any door that has been removed (AP23699, p. 14).
• For repairs to the gas control, burners or other safety devices, which the manual refers to qualified service personnel (AP23699, p. 25).

Related codes: 10 blinks, 9 flashes, 9-2 flashes. All Rheem gas tank water heaters codes

Rheem power vent water heater 3 flashes: pressure switch open

Checked October 2026

Short answer On Rheem power vent and induced draft tanks, three gas valve LED flashes mean a pressure switch failed open; on powered damper tanks, the flue damper switch is open. Fixes are technician work; power vent owners can check the outdoor vent terminal. See what to check

What it means

Three flashes is the code for a switch that failed open. On power vent models, the control checks the blower vacuum switch at start-up and on each call for heat: it verifies that the switch is open, runs the blower for a pre-purge of about 5 seconds, and then verifies that the switch has closed, “ensuring that the blower is functioning properly and that the venting system is not blocked” (AP22511 Rev 02, p. 31). Which switch the code names depends on the manual:

• Power vent: “Pressure and/or blower thermal switch failed open.”, LCD code 46 on models with the optional display. The table’s fixes: verify that the wiring to the blower pressure switch and thermal switch is correct and properly connected, check the vent system for blockage or obstructions, and replace the blower assembly (AP22511 Rev 02, p. 37).
• Induced draft, and the Ruud Ultra Low NOx manual AP19361 (12/17): “Pressure switch failed open.” Its causes are “Vent blockage or improper installation, switch tube blockage, faulty switch, blower improper operation or temperature switch open” (AP15696-3, p. 28; AP19361, p. 32).
• Powered damper: “System in Lockout/Flue Damper Switch open”. Its causes include an improperly installed damper, a damper switch stuck open or faulty, incorrect wiring, a faulty damper motor, and obstruction or debris in the damper opening (AP15756, p. 24).

Check these first

The power vent manual gives the owner part of the vent check as routine maintenance:

1. If you smell gas, stop and follow the steps at the top of this page.
2. Check the outdoor vent terminal “to see that it is free of obstructions, and that there is no damage nearby caused by condensate” (AP22511 Rev 02, p. 32). In applicable climates, the manual also says to inspect the vent and air-inlet terminals for snow (AP22511 Rev 02, p. 33).
3. Inspect the dilution air inlet and the combustion air inlet openings, make certain no blockage exists, and clean any lint, dirt or oil accumulation; clean the screens in the vent terminal if it has them (AP22511 Rev 02, p. 32).
4. If the vent may be blocked beyond what you can see, the manual’s chart says to “Contact a qualified service technician to evaluate vent system for blockage.” (AP22511 Rev 02, p. 35).

In the powered damper and induced draft manuals, the three-flash rows list only technician fixes; the powered damper row ends with “Contact a qualified service technician.” (AP15756, p. 24).

When to call a licensed technician

• Wiring to the pressure switch, thermal switch or flue damper switch, the switch tube, and the switches themselves (AP22511 Rev 02, p. 37; AP15696-3, p. 28; AP15756, p. 24).
• Replacing the blower assembly or the blower temperature switch (AP22511 Rev 02, p. 37; AP15696-3, p. 28), or the flue damper assembly (AP15756, p. 24).
• Evaluating the vent system for blockage or improper installation (AP22511 Rev 02, p. 35).

The power vent table sits under cautions about servicing controls and not attempting repair of the vent system or other safety devices (AP22511 Rev 02, p. 37).

Related codes: 6-2 flashes, 2 flashes, ● ○ ● ○ ○ ●. All Rheem gas tank water heaters codes

Rheem power vent water heater 6-1 flashes: failed to light

Checked October 2026

Short answer On Rheem power vent, induced draft and powered damper tanks, six flashes of one mean the heater failed to light. The tables name gas supply problems and the pilot; pilot and gas control work is for a technician. See what to check

What it means

The manuals print this gas valve LED code as “Six flashes of one, every three seconds” (power vent) and as “Six-One Flash” or “Six-One Flashes” with a three-second pause (induced draft and powered damper) (AP22511 Rev 02, p. 37; AP15696-3, p. 28; AP15756, p. 24).

On power vent models the pilot is lit by a spark, and the main gas valve opens only once the pilot flame is established (AP22511 Rev 02, p. 31). The manual adds: “If no main burner flame is established, the gas control will go through three trials for ignition before going into a lock-out. A warning light will alert the user of this lock-out condition.” It then sends you to its troubleshooting guide (AP22511 Rev 02, p. 29). The wording of the code:

• Power vent: “System in lockout. Failed trial for ignitions.”, LCD code 11 on models with the optional display. The table’s fixes, in order: the gas supply is off or too low to operate, so turn on the gas supply and/or increase the inlet gas supply pressure; replace the pilot assembly; replace the combination gas control (thermostat) (AP22511 Rev 02, p. 37).
• Induced draft, and the Ruud Ultra Low NOx manual AP19361 (12/17): “Failed trial for ignition”, caused by “Insufficient gas supply, unstable pilot, carbon buildup on electrode or wire/pilot tube damage”; fixes “Check gas supply” and “Replace pilot” (AP15696-3, p. 28; AP19361, p. 32).
• Powered damper: “System in Lockout/ Unit failed to light”. Its causes are an unstable pilot flame, a restricted or damaged pilot tube, carbon build-up on the pilot’s electrode, a damaged pilot igniter wire and gas supply problems; fixes “Replace Pilot assembly” and “Correct gas supply” (AP15756, p. 24).

Check these first

1. If you smell gas, stop and follow the steps at the top of this page.
2. Make sure the gas supply to the heater is on. The power vent table’s first fix is “Gas supply is off or too low to operate. Turn on the gas supply and/or increase the inlet gas supply pressure.” (AP22511 Rev 02, p. 37). Raising the inlet gas supply pressure is not an owner step.
3. The owner’s operating procedure is the label on the heater. The power vent label’s steps use the ON/OFF switch on the gas control, the electric power and a five-minute wait to clear out any gas, and it says not to light the pilot by hand. “If the appliance will not operate, follow the instructions “TO TURN OFF GAS TO APPLIANCE” and call your service technician or gas supplier.” (AP22511 Rev 02, p. 28). The powered damper label ends the same way (AP15756, p. 17).

When to call a licensed technician

• When the heater does not operate after the label’s steps (AP22511 Rev 02, p. 28).
• For low inlet gas pressure, the pilot assembly, the pilot tube and electrode, the igniter wire, and the gas control (AP22511 Rev 02, p. 37; AP15696-3, p. 28; AP15756, p. 24).
• For air in the gas line. The power vent chart sends “Unable to light the main burner” with air in the gas line to “a qualified service technician to purge the air from the gas line.” (AP22511 Rev 02, p. 35).

The power vent table sits under the caution not to attempt repair of gas piping, the gas control, burners, the vent system or other safety devices (AP22511 Rev 02, p. 37).

Related codes: 6-5 flashes, 6-3 flashes, 1 flash. All Rheem gas tank water heaters codes

Rheem power vent water heater 7 flashes: flammable vapor lockout

Checked October 2026

Short answer On Rheem, Ruud and Richmond power vent, powered damper and induced draft tanks, seven gas valve LED flashes mean a flammable vapor sensor lockout. The manuals tell the owner to promptly contact a qualified service technician. Status light models use seven blinks differently. See what to check

What it means

These tanks have a flammable vapor sensor that the electronic control watches in all modes of operation. When it detects flammable vapors, the control shuts the heater down and keeps it from being started again (AP22511 Rev 02, p. 31). Seven flashes of the gas valve LED is that lockout. The wording differs by manual:

• Power vent: “System in lockout. Flammable vapor sensor.”, shown as LCD code 47 on models with the optional display (AP22511 Rev 02, p. 37).
• Powered damper: “System in Lockout/ Presence of Flammable Vapors detected”. The table’s causes are gasoline or other flammable vapors, a faulty flammable vapor sensor or a faulty gas control (thermostat) (AP15756, p. 25).
• Induced draft, and the Ruud Ultra Low NOx manual AP19361 (12/17): “Flammable vapor sensor lockout”, caused by “Gasoline or other flammable gas was detected near the appliance or the sensor has failed” (AP15696, p. 28; AP19361, p. 32).

The power vent manual lists what sets the sensor off: vapors of gasoline; vapors of certain flammable paints, stains and thinners; vapors of vent pipe cement and solvents; bleach in direct contact with the sensor; and some other flammable materials and their vapors (AP22511 Rev 02, p. 31).

The powered damper manual explains why the heater stays off. Air movement can carry flammable vapors some distance, and the pilot or main burner can ignite them and “create a shut down condition of the water heater which will not allow the water heater to ignite until examined by a Qualified Service Technician” (AP15756, p. 7).

Check these first

The power vent manual gives the owner this instruction: “If the flammable vapor sensor shuts down the water heater, then the electronic control will display the appropriate error code and you should then promptly contact a qualified service technician.” (AP22511 Rev 02, p. 31). Page 3 of the power vent and induced draft manuals adds three things: clear any hazardous materials and ventilate the area around the water heater; do not turn off the appliance or adjust the ON/OFF switch in any way; do not tamper with the flammable vapor sensor (AP22511 Rev 02, p. 3; AP15696 (11/10), p. 3; AP15696-3, p. 3; AP19361, p. 3). What else they say:

1. If you smell gas, stop and follow the steps at the top of this page.
2. Contact a qualified service technician. Page 3 of the power vent and induced draft manuals says it too: “If the flammable vapor sensor shuts down the water heater, contact a qualified service technician.” (AP22511 Rev 02, p. 3; AP15696, p. 3; AP19361, p. 3). The powered damper manual says the same about its combustion shut off device (AP15756, p. 20).
3. Do not store or use gasoline or other flammable vapors and liquids, such as adhesives or paint thinner, near the heater. If such flammables must be used, the manual says to open doors and windows for ventilation and to shut off all gas burning appliances nearby, including their pilot burners (AP22511 Rev 02, p. 29).
4. Do not block the flammable vapor sensor, and keep water, solvents and cleaning agents off it. The manual says it needs no maintenance or cleaning (AP22511 Rev 02, p. 33).

When to call a licensed technician

• For every seven-flash lockout, as above (AP22511 Rev 02, p. 31).
• The gas valve LED table sits under cautions about servicing controls and not attempting repair of the gas control. For power vent models it lists three steps: verify that no gasoline or flammable vapors are present, reset the combination gas control (thermostat), and replace the flammable vapor sensor (AP22511 Rev 02, p. 37). The powered damper table resets the gas control with the “ON/OFF” switch on its front and adds replacing the gas control (AP15756, p. 25). The owner’s sections of the same manuals do not hand the reset to the owner; they send the shutdown to a technician.
• 8-1 flashes is a different code, a fault in the sensor itself: “Flammable vapor sensor, fault detected.” on power vent models, fixed by replacing the sensor or the gas control (AP22511 Rev 02, p. 37).

Related codes: 8-1 flashes, ● ○ ○ ○ ○ ●, ● ○ ○ ● ○ ●. All Rheem gas tank water heaters codes

Rheem Maximus A001: ignition lockout, what to check

Checked October 2026

Short answer A001 is an ignition lockout on Rheem, Ruud and Richmond super high efficiency tanks: 9 failed ignitions in the use and care manuals, 27 in the service manual. Turn the unit off and on; if it persists, contact technical support or a service provider. See what to check

What it means

A001 is an alarm. Rheem’s table describes it as “Ignition lockout due to a total of 9 consecutive failed ignitions. This will disable the heater.” The alarm screen reads “A001 Ignition lockout.” with the instruction “Clear error code by turning the unit off/on. If problem persists, contact technical support or service provider.” (AP21833 Rev 02, p. 42). AP21831 Rev 02 and AP23779 print the same row on p. 42, and the service manual AP23008 Rev 03 on p. 35.

The service manual describes a longer sequence than the 9 in its own code table: after 9 failed ignition attempts the control shows alert T029 and waits 30 minutes; after two more rounds of 9, 27 consecutive failed attempts in all, it shows A001 and stays locked out until the power is cycled (AP23008 Rev 03, pp. 31, 32, 47). The use and care manuals give only the count of 9.

The table’s other codes help place it. T029, an alert, is “Unit did not light.” and its screen reads “T029 Failed ignition. Retrying.” (AP21833 Rev 02, p. 44). A001 is the alarm that disables the heater (AP21833 Rev 02, p. 42). T029 is the alert shown while the control is still retrying.

You find the code on the touchscreen. With an active alarm the “Service” button blinks on the home screen; pressing it shows the active alarms and the alarm history, and “more info” gives a longer explanation (AP21833 Rev 02, pp. 37–38).

Check these first

1. If you smell gas, stop and follow the steps at the top of this page.
2. Clear the code by turning the unit off and on, as the alarm screen says (AP21833 Rev 02, p. 42). The manual’s chart refers to the unit’s “ON/OFF” switch (AP21833 Rev 02, p. 41).
3. If the burner still will not light, the chart’s first row is air in the gas line: “Let the unit cycle at least 3 times to remove air from the gas line. If the unit does not try to light, contact a qualified service technician to purge the air from the gas line.” (AP21833 Rev 02, p. 40).
4. The next row is the gas valves: “Check to make sure that all manual shut-off valves between the unit and the gas line are open.” (AP21833 Rev 02, p. 40).
5. If A001 persists, contact technical support or a service provider, as the screen says (AP21833 Rev 02, p. 42).

When to call a licensed technician

• A001 that comes back after the off and on (AP21833 Rev 02, p. 42).
• The other causes in the chart for a main burner that will not light: a blocked inlet or exhaust vent pipe, the pressure switch and its hoses, wire connections that are not fully secured, and a gas control problem (AP21833 Rev 02, pp. 40–41). Apart from making sure the pressure switch hoses are not kinked or disconnected, these are checks for a qualified service technician.
• Grounding. The chart says to verify that the electrical supply line and the unit have a proper ground connection (AP21833 Rev 02, p. 41).
• Anything behind the protective cover. The manual says to make certain power to the water heater is off before removing it for any reason, and not to attempt repair of gas piping, the gas control, the burner, vent connectors or other safety devices (AP21833 Rev 02, p. 41).

Related codes: A002, T029, A030. All Rheem gas tank water heaters codes