York furnace 4 red flashes: limit switch open (Coleman, Luxaire)

Short answer On York, Coleman and Luxaire furnaces, 4 red flashes mean the main limit switch has opened; the modulating models word it differently, see the table below. The owner's manual has no step for this code, and the installation manuals' checks are technician work. See what to check

Furnace control LED

4 red flashes

“Airflow problem OR open fuse”

Technician

Printed on 25 model series · 12 documents

TM8X, TMLX, TM9E, TM9T, TG9S, GG9S, TM9X, TP9C, YP9C, CP9C, LP9C, TM9V, DGAX, TM8V*C, TMLV*C, TM8T*MP, TMLT*MP, TG8S*MP, TGLS*MP, GG8S*MP, GGLS*MP, TPLC*C, YPLC*C, CPLC*C, LPLC*C · 998492-UIM-C-1013 p. 26; 1083163-UIM-A-0214 p. 38; 1083286-UIM-A-0114 p. 39; 1083287-UIM-A-0114 p. 40; 1083288-UIM-A-0114 p. 38; 5750151-UIM-G-0423 p. 39; 1083294-UIM-A-0114 p. 44; 5483101-UIM-A-1118 p. 29; 1034867-UIM-B-0913 p. 31; 995472-UIM-B-0713 p. 28; 998491-UIM-B-1013 p. 29; 987158-UIM-B-1013 p. 32

The lamp blinks 4 times, then pauses. It shows the count only; the timing on your board may differ.

What it means

On most York, Coleman and Luxaire furnaces, 4 red flashes mean the main limit switch has opened its normally closed contacts. While it is open, the control runs the supply air blower and the inducer (5750149-UIM-I-0423, p. 38; 6100757-UIM-C-1124, p. 58). The label printed with the wiring diagram shortens this to “Airflow problem” or “Airflow problem OR open fuse” (5750149-UIM-I-0423, p. 40; 1083294-UIM-A-0114, p. 44). On the Y81E, RL18, Y82E, Y91E, RG19, Y92E and Y92V the label reads “LS / ROS SWITCH OPEN”; the Y92V wiring-diagram legend spells out LS as limit switch and ROS as rollout switch (6125049-UIM-C-0624, p. 52; 6553957-UIM-A-0626, p. 96).

Most installation manuals name the causes to check: a dirty filter, a duct system of the wrong size, an incorrect blower speed setting or firing rate, loose limit switch wiring, or a faulty blower motor (5750149-UIM-I-0423, p. 38).

What follows depends on how long the limit stays open and how often it opens:

• If the limit has not closed within 5 minutes, the control treats the blower as not working, starts a hard lockout and begins to flash 11 red flashes (5750149-UIM-I-0423, p. 38; 6125049-UIM-C-0624, p. 49).
• On the TM9V*C, TM9V, TM8V*C, TM9T, TM8T*MP and Y92V, if the limit is still open after 15 minutes, the control treats it as an opened manual-reset rollout switch and begins to flash 5 red flashes (5750149-UIM-I-0423, p. 38; 1083286-UIM-A-0114, p. 37; 6553957-UIM-A-0626, p. 88).
• If the main limit opens five times within one call for heat, most of the manuals say the control shows 4 red flashes and enters a one-hour soft lockout (5750149-UIM-I-0423, p. 38; 6125049-UIM-C-0624, p. 49). The Y92V table does not have this sentence (6553957-UIM-A-0626, p. 88).

The modulating furnaces word the code differently. On the YP9C, CP9C, LP9C, TP9C and the TPLC, YPLC, CPLC, LPLC it covers an open high limit switch, a defective temperature sensor or an open 24 volt fuse. The causes named are a dirty air filter, a duct system of the wrong size, a faulty blower motor, restricted circulating airflow or an open fuse on the control board (5750151-UIM-G-0423, p. 36; 987158-UIM-B-1013, p. 30). On the TM9M it is “a primary or auxiliary limit switch”, and a blown fuse on the circuit board can cause it too (1083293-UIM-A-0114, p. 39). These manuals do not say that the code turns into 11 or 5 red flashes.

Check these first

The owner’s manuals 1010352-UUM-O-0423 and 6100761-UUM-C-1124 have no entry for 4 red flashes. The only red pattern they list is “Rapid red flashes”, with the instruction to contact your local dealer, contractor, or service provider (1010352-UUM-O-0423, p. 5). The LED is behind a clear view port in the blower compartment door (1010352-UUM-O-0423, p. 5).

For a furnace that is not operating correctly, the manual lists visual checks to make before that call. They are the same for every code. In the manual’s order:

1. Check that electrical power to the furnace is turned on (1010352-UUM-O-0423, p. 5).
2. Check that the manual gas shut-off valve in the gas piping supply is in the on position (1010352-UUM-O-0423, p. 5).
3. Check that the on/off switch on the gas valve is in the on position (1010352-UUM-O-0423, p. 5). The manual reaches this switch by setting the thermostat to its lowest setting, turning off all electric power to the appliance and removing the furnace burner access panel or door (1010352-UUM-O-0423, p. 4). Use only your hand on the switch, never tools; if it does not move by hand, do not try to repair it, and call a qualified service technician (1010352-UUM-O-0423, p. 3). Turning it back on follows the full operating instructions: turning the furnace off and on.
4. Check that the furnace blower access panel or door is correctly positioned. The electrical power supply is cut off if this door is removed (1010352-UUM-O-0423, p. 5).

6100761-UUM-C-1124 lists the same checks (pp. 10–11).

A dirty filter heads the installation manuals’ list of causes (5750149-UIM-I-0423, p. 38). Filters are what the owner’s manual covers under user maintenance. They must be installed outside the furnace casing, for example in a rack on the casing or in the return air duct; if the location or the replacement process is not obvious, contact your installer or service technician (1010352-UUM-O-0423, p. 4). High-velocity filters can be cleaned with a vacuum cleaner or washed with a garden hose and must dry completely before they go back in; throwaway filters are replaced with new filters of the same size (1010352-UUM-O-0423, p. 5). Before user maintenance, 6100761-UUM-C-1124 says to make sure the area is well ventilated, turn the thermostat off, wait for a running blower to stop, turn off the gas and electrical power supplies to the furnace, and let metal parts cool to room temperature (6100761-UUM-C-1124, p. 9). The filter section is not tied to this code.

When to call a licensed technician

The checks in the installation manuals belong to a technician:

• The duct system, the blower speed setting, the firing rate, the limit switch wiring and the blower motor (5750149-UIM-I-0423, p. 38).
• On the modulating furnaces, the temperature sensor and the fuse on the control board (5750151-UIM-G-0423, p. 36).
• A hard lockout. The installation manuals reset it by turning power to the control off and back on after the problem has been corrected (5750149-UIM-I-0423, p. 38); the owner’s manuals do not describe a reset.

Call as well if 4 red flashes keep coming back, or if the code changes to 11 or 5 red flashes. The owner’s manual says the user must not purchase, install, or replace any components of the furnace (1010352-UUM-O-0423, p. 5).

Notes for different models

Series	Label on the wiring diagram	Installation manual text	Source
TM9V*C; TM8V*C, TMLV*C (2013 and 2023); TM9V (2014); TM9T; TM8T*MP, TMLT*MP	“Airflow problem” (TM9V*C, TM8V*C 2023); “Airflow problem OR open fuse” (the others)	Main limit open; after 5 min hard lockout and 11 red flashes; after 15 min 5 red flashes; five openings in one call for heat, 1-hour soft lockout	5750149-UIM-I-0423, pp. 38, 40; 5750148-UIM-D-0423, pp. 26, 30; 1034867-UIM-B-0913, pp. 28, 31; 1083294-UIM-A-0114, pp. 41, 44; 1083286-UIM-A-0114, pp. 37, 39; 995472-UIM-B-0713, pp. 26, 28
TG9S, GG9S; TM9X; TM9E (2014 and 2023); RGF19*E; TM9Y; TG8S*MP, TGLS*MP, GG8S*MP, GGLS*MP; TM8X, TMLX	“Airflow problem OR open fuse” (2013–2014 manuals); “Airflow problem” (TM9E 2023, RGF19*E, TM9Y)	Main limit open; after 5 min hard lockout and 11 red flashes; five openings, 1-hour soft lockout; no 15-minute step	1083287-UIM-A-0114, pp. 38, 40; 1083288-UIM-A-0114, pp. 36, 38; 1083163-UIM-A-0214, pp. 36, 38; 6019630-UIM-F-0423, pp. 33, 36; 6019627-UIM-F-0423, pp. 33, 36; 5750144-UIM-H-0423, pp. 35, 37; 998491-UIM-B-1013, pp. 27, 29; 998492-UIM-C-1013, pp. 24, 26
Y81E, RL18, Y82E, Y91E, RG19, Y92E	“LS / ROS SWITCH OPEN”	Same as the row above	6100757-UIM-C-1124, pp. 58, 62; 6100760-UIM-C-1124, pp. 58, 62; 6142403-UIM-C-1124, pp. 59, 63; 6125049-UIM-C-0624, pp. 49, 52; 6125051-UIM-C-0624, pp. 49, 52; 6154201-UIM-B-1224, pp. 77, 82
Y92V	“LS / ROS SWITCH OPEN”, display 04	Main limit open; after 5 min hard lockout and 11 red flashes; after 15 min 5 red flashes	6553957-UIM-A-0626, pp. 88, 96
YP9C, CP9C, LP9C, TP9C; TPLC*C, YPLC*C, CPLC*C, LPLC*C	“Airflow problem OR open fuse” (5750151-UIM-G-0423, 987158-UIM-B-1013); “Airflow problem” (1083292-UIM-A-0114)	“High limit switch open or defective temperature sensor or 24 volt fuse is open.”	5750151-UIM-G-0423, pp. 36, 39; 1083292-UIM-A-0114, pp. 41, 43; 987158-UIM-B-1013, pp. 30, 32
TM9M	“Airflow problem”	Primary or auxiliary limit switch open; a blown fuse on the circuit board can also cause it	1083293-UIM-A-0114, pp. 39, 41
DGAX	“Airflow problem OR open fuse”	No text; label only	5483101-UIM-A-1118, p. 29
DGAA, DGAH (owner’s manual, green LED)	4 FLASH	Limit switch open: a primary or auxiliary limit switch has opened	5165697-BUM-C-0818, p. 8

The DGAA and DGAH manual is for furnaces in manufactured homes. Its 60-minute automatic reset covers fault 4 (5165697-BUM-C-0818, p. 8). Its service section, written for a qualified service agency, describes two limit switches, the upper one with a manual reset, and says the homeowner must never attempt service or maintenance on the appliance (5165697-BUM-C-0818, p. 6).

Related York, Coleman and Luxaire codes

• 11 red flashes “Check blower motor/wiring”
• 5 red flashes “Flame Rollout OR open fuse”

See also

• Heat pump vs gas calculator
• Furnace and HVAC tax credits for 2025 and 2026: 25C ended after 2025
• Form 5695 for 2025 and 2026: QMID, lines, carryforward
• How a gas furnace lights, and how the control board blinks a failure code
• Home maintenance schedule from the manuals: monthly to yearly
• Winter home maintenance checklist: furnace, boiler, water heater
• Water heater or furnace closet: clearance and air requirements

Other gas furnaces: Carrier, Goodman, Lennox, Rheem furnaces, Trane and American Standard

All York, Coleman and Luxaire codes

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