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Comfortmaker Furnace Error Codes — Complete Guide

Every documented Comfortmaker furnace error code with causes, fixes, and the parts you may need. Also covers: Tempstar, Comfortmaker, Day and Night, Arcoaire, KeepRite (all ICP brands).

How to read Comfortmaker error codes:
Comfortmaker, Tempstar, Comfortmaker, Day and Night, Arcoaire, and KeepRite furnaces (all ICP/Carrier Global brands) use a flash count system. Count the red LED flashes on the control board.

All Comfortmaker Error Codes

Steady ON

Control Board Failure

Internal board fault.

DIY check: Power cycle. Replace board if solid ON persists.

Common part needed: Shop Control Board →

Steady OFF

No Power

No power to board.

DIY check: Check breaker, switch, door switch, fuse, transformer.

Common part needed: Shop Transformer →

1 Flash

Open Limit / Rollout

High limit or flame rollout switch has opened.

DIY check: Check air filter, registers, blower operation. If rollout tripped, call technician.

Common part needed: Shop Fan Motor →

2 Flashes

Pressure Switch Stuck Closed

Pressure switch is closed before inducer runs.

DIY check: Check for stuck switch, water in hose.

Common part needed: Shop Pressure Switch →

3 Flashes

Pressure Switch Open

Pressure switch did not close.

DIY check: Check condensate drain, vent, hose, inducer motor.

Common part needed: Shop Pressure Switch →

4 Flashes

Open Secondary Fuse

Board fuse blown.

DIY check: Fix short circuit, then replace fuse.

Common part needed: Shop Transformer →

5 Flashes

Flame Without Gas Valve

Flame detected when gas should be off.

DIY check: Turn off gas, call technician.

Common part needed: Shop Gas Valve →

6 Flashes

Power Reversed

115V polarity reversed.

DIY check: Correct wiring polarity.

7 Flashes

Gas Valve Error

Gas valve circuit fault.

DIY check: Check valve wiring and coil. May need replacement.

Common part needed: Shop Gas Valve →

8 Flashes

Low Flame / Ignition Failure

Weak flame signal or ignition failure.

DIY check: Clean flame sensor. Check igniter and gas supply.

Common part needed: Shop Flame Sensor →

When to call a technician

If the same code keeps coming back after you have addressed the obvious cause (dirty filter, flame sensor, etc.), or if you smell gas, see burn marks, or the furnace will not come out of lockout after a power cycle, call a licensed HVAC technician. Electrical and gas work carries real safety risk.

FAQ

How do I reset my Comfortmaker furnace after an error code?

Turn the furnace power off at the switch or breaker for 30 seconds, then turn it back on. The control board will clear the lockout and attempt to restart. If the same code returns, the underlying problem has not been fixed.

My Comfortmaker furnace shows no LED light at all

No light means no power to the control board. Check: the furnace switch is on, the breaker is not tripped, and the door safety switch is engaged (the furnace door must be fully closed). If all three check out, the control board or transformer may have failed.

Can I fix Comfortmaker error codes myself?

Many codes point to simple fixes: replacing a dirty filter (codes related to overheating), cleaning the flame sensor (codes related to flame proving), or clearing a blocked condensate drain (pressure switch codes). Anything involving gas lines, wiring, or the heat exchanger should be left to a licensed technician.

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Comfortmaker Furnace Error Codes — Complete Guide

All Comfortmaker Error Codes

When to call a technician

FAQ