Heil Furnaces Error Codes

1 FLASH

Heil furnace status LED flashes 1 time repeatedly; furnace will not start heating cycle.

Ignition Failure / Lockout

10 FLASH

Heil furnace LED flashes 10 times; furnace may lock out after repeated ignition attempts.

Gas Valve Error / Gas Flow Fault

11 FLASH

Heil furnace LED flashes 11 times; furnace may not start or may shut down due to internal control fault.

Internal Control Board Fault

12 FLASH

Heil furnace LED flashes 12 times; blower may run unexpectedly or not at all, and heating cycles may be erratic.

Blower Calibration / Blower On After Power Up

13 FLASH

Heil furnace LED flashes 13 times; furnace may short-cycle or shut down on limit frequently.

Limit Circuit Lockout / Repeated Limit Trips

14 FLASH

Heil furnace LED flashes 14 times; furnace may not start or may shut down due to ignition lockout.

Ignition Lockout (Exceeded Retries)

2 FLASH

Heil furnace LED flashes 2 times; inducer runs but burners do not light, or furnace shuts down shortly after starting.

Pressure Switch Stuck Closed

3 FLASH

Heil furnace LED flashes 3 times; inducer runs but pressure switch does not close, furnace does not ignite.

Pressure Switch Stuck Open / Venting Problem

31

Heil furnace LED shows code 31; inducer may run but pressure switch does not close, or furnace shuts down on pressure fault.

Pressure Switch Did Not Close or Reopened

33

Heil furnace LED shows code 33; furnace shuts down on limit and blower may continue to run.

Limit or Flame Rollout Switch Open

34

Heil furnace LED shows code 34; ignition fails or flame is lost shortly after lighting.

Ignition Proving Failure

4 FLASH

Heil furnace LED flashes 4 times; burners ignite but shut off quickly, or furnace cycles repeatedly without heating properly.

Open High Limit Switch

41

Heil furnace LED shows code 41; indoor blower may not start or runs at incorrect speed.

Blower Motor Fault (ECM or PSC)

42

Heil furnace LED shows code 42; furnace may not respond correctly to thermostat calls, especially in dual-fuel or communicating setups.

Inducer or Communication Fault

43

Heil furnace LED shows code 43; furnace may not stage correctly or may not reach full capacity.

Secondary Heat Stage Fault

44

Heil furnace LED shows code 44; furnace may shut down unexpectedly or not start due to flame sensing issues.

Flame Sense Out of Range

45

Heil furnace LED shows code 45; furnace may lock out after multiple faults.

Control Lockout (Too Many Faults)

5 FLASH

Heil furnace LED flashes 5 times; furnace may start but shuts down, or will not start, often associated with rollout or flame safety issues.

Flame Rollout Switch Open

6 FLASH

Heil furnace LED flashes 6 times; furnace may not respond to thermostat or may run erratically.

Polarity / Ground Fault or 115V Line Problem

7 FLASH

Heil furnace LED flashes 7 times; furnace may lock out, often after repeated failed ignition attempts.

Flame Sense Fault / Flame Detected with Gas Off

8 FLASH

Heil furnace LED flashes 8 times; furnace may not start or may shut down unexpectedly, often related to low-voltage issues.

Low Voltage / Secondary Fuse Open

9 FLASH

Heil furnace LED flashes 9 times; furnace may not respond to thermostat or may behave erratically.

Reversed 24V Polarity / Incorrect Wiring

Symptom

Furnace blower is noisy with a high-pitched squeal or grinding sound.

Blower Bearing or Motor Failure

Symptom

Furnace burners light but go out after a few seconds; this repeats several times.

Flame Sensing / Proving Failure

Symptom

Furnace causes noticeable vibration or rattling noises during operation.

Mechanical Vibration / Loose Components

Symptom

Furnace cycles on and off with blower running but produces cool or only slightly warm air.

Blower Running Without Proper Burner Operation

Symptom

Furnace ignitor glows but burners do not light.

No Gas Flow to Burners

Symptom

Furnace intermittently trips the household circuit breaker.

Overcurrent / Electrical Short

Symptom

Furnace makes loud booming or delayed ignition noise when burners light.

Delayed Ignition

Symptom

Furnace produces unusual odors when running, such as burning dust or metallic smell.

Odor / Contamination in Heat Exchanger or Ducts

Symptom

Furnace runs but carbon monoxide detector in the home alarms during operation.

Combustion / Venting Hazard

Symptom

Furnace runs but delivers insufficient heat; home never reaches thermostat setpoint.

Underfiring / Low Heat Output

Symptom

Furnace short cycles: starts, runs briefly, then shuts off and restarts frequently.

Short Cycling

Symptom

Furnace starts and runs but shuts off on very cold days, sometimes with ice on vent termination.

Vent Icing / Condensate Freezing

Symptom

Furnace will not start at all; no inducer, no blower, no LED lights.

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 runs continuously but burners do not light.

Stuck Pressure Switch or Failed Ignition Sequence

Symptom

Thermostat calls for heat but furnace does not respond; LED shows normal idle or no fault.

No Heat Call Reaching Furnace

Symptom

Water leaking around the base of a high-efficiency Heil furnace.

Condensate Leak