Comfortmaker Furnaces Error Codes

11

Furnace attempts to start but shuts down quickly; LED flashes code 11 (no previous code stored).

No Previous Fault Stored / Normal Power-Up Indication

12

LED flashes code 12; blower runs briefly at power-up, then furnace may or may not start normally.

Blower On After Power-Up / Normal Post-Power-Up Sequence

13

LED flashes code 13; furnace may shut down and blower may run continuously or for an extended period.

Limit Switch Lockout / Flame Rollout or High-Temperature Lockout

14

LED flashes code 14; furnace locks out after failed ignition attempts, may retry after an hour.

Ignition Lockout (Failed Ignition Attempts)

21

LED flashes code 21; furnace may not respond properly to thermostat commands.

Gas Heating Lockout or Thermostat Signal Fault (depending on board revision)

22

LED flashes code 22; furnace may not start inducer or may behave erratically.

Abnormal Flame-Proving Signal / Flame Detected When No Call for Heat

23

LED flashes code 23; furnace may not respond to thermostat or may cycle oddly.

Pressure Switch or Inducer Fault (board-specific diagnostic code)

24

LED flashes code 24; furnace may not start or may show low-voltage issues.

Secondary (24V) Fuse Open / Low-Voltage Short

31

LED flashes code 31; furnace will not ignite, inducer may run but pressure switch does not prove.

Pressure Switch Open / Draft Problem

32

LED flashes code 32; furnace may run blower unexpectedly or fail to start a heat cycle.

Low Heat or High Heat Pressure Switch Fault / Partial Restriction

33

LED flashes code 33; furnace shuts down on high limit, blower may run continuously.

High Limit Switch Open / Overheating

34

LED flashes code 34; furnace attempts ignition but burners do not light or light briefly then go out.

Ignition Proving Failure / Flame Not Detected

41

LED flashes code 41; blower may run at incorrect speed or airflow seems low/high.

Blower Motor Fault / Incorrect Blower Speed

42

LED flashes code 42; blower may not start or may run at wrong times.

Inducer or Blower Relay Fault / Control Board Output Error

43

LED flashes code 43; furnace may short-cycle or fail to maintain flame.

Gas Valve or Flame Sense Control Fault

44

LED flashes code 44; furnace may lock out or show erratic ignition behavior.

Ignition Control Fault / Reversed Polarity or Ground Issue

45

LED flashes code 45; furnace may lock out after multiple failed attempts.

Control Board Lockout / Multiple Faults Detected

Symptom

Burners light but go out after a few seconds; furnace repeatedly tries to restart.

Flame Sensing Failure

Symptom

Furnace blower starts and stops repeatedly without burner ignition; cool air may blow briefly.

Fan-Only Cycling / Control Board or Limit Issue

Symptom

Furnace causes lights to dim or flicker when starting.

High Inrush Current / Electrical Supply Issue

Symptom

Furnace cycles on and off rapidly (every few minutes) without maintaining temperature.

Rapid Short Cycling

Symptom

Furnace frequently trips the household circuit breaker.

Overcurrent / Electrical Short

Symptom

Furnace is very old and heat exchanger shows signs of rust, cracks, or soot buildup.

Heat Exchanger Deterioration

Symptom

Furnace makes loud banging or booming noise at startup when burners ignite.

Delayed Ignition

Symptom

Furnace makes loud rattling or scraping noises from the blower compartment during operation.

Blower Wheel or Motor Problem

Symptom

Furnace or ductwork vibrates excessively and is noisy when the blower runs.

Excessive Vibration / Duct Resonance

Symptom

Furnace produces a high-pitched whine or loud rumbling from the inducer area.

Inducer Motor Bearing Failure or Blocked Draft Path

Symptom

Furnace runs but produces insufficient heat; supply air feels lukewarm and house never reaches set temperature.

Low Heat Output

Symptom

Furnace runs but some rooms are too hot while others are too cold.

Uneven Heating / Air Distribution Problem

Symptom

Furnace starts and runs but shuts off before reaching the thermostat set temperature; frequent short cycles.

Short Cycling / Overheating or Oversized Furnace

Symptom

Furnace will not start at all; no inducer, no blower, no LED lights on the Comfortmaker control board.

No Power to Furnace

Symptom

Indoor blower runs continuously even when thermostat is not calling for heat or fan.

Blower Stuck On

Symptom

Inducer motor starts but burners never light; you hear clicking or see ignitor glow, then system shuts down.

Ignition Failure Without Stored Code

Symptom

Persistent metallic or electrical burning smell during furnace operation.

Overheating Electrical Component or Motor

Symptom

Rust stains or water marks inside the furnace cabinet or on the burner area.

Internal Condensation or Humidifier Leak

Symptom

Strong burning dust smell when the furnace first starts for the season.

Dust Burn-Off

Symptom

Thermostat calls for heat but furnace does nothing; control board LED is on and steady, no error code.

No Call for Heat Reaching Control Board

Symptom

Water leaking around the base of the Comfortmaker furnace or onto the floor nearby.

Condensate Leak (Condensing Furnace)