Fraser-Johnston Furnaces Error Codes

1 FLASH

Furnace will not start; inducer motor does not run; LED on control board flashes once repeatedly.

Ignition Failure Lockout

2 FLASH

Furnace starts inducer but pressure switch does not close; LED on control board flashes twice repeatedly; burners do not light.

Pressure Switch Open Fault

3 FLASH

Inducer runs, ignitor glows, burners light briefly then go out; LED flashes three times repeatedly.

Pressure Switch Stuck Closed or Opens During Run

4 FLASH

Furnace attempts ignition but shuts down; LED flashes four times repeatedly; blower may run for a short purge cycle.

Open High Limit Switch

5 FLASH

Furnace does not respond to thermostat; LED flashes five times repeatedly; no inducer or blower operation.

Flame Sensed With Gas Valve Off (False Flame) or Rollout/Open Safety

6 FLASH

Inducer and blower may run; LED flashes six times repeatedly; furnace does not heat.

Pressure Switch Cycle Fault or Vent Blockage Lockout

7 FLASH

Furnace does not start; LED flashes seven times repeatedly; blower may run continuously.

Flame Rollout Switch Open

8 FLASH

Blower runs continuously; no heat; LED flashes eight times repeatedly.

Low Heat or High Heat Limit Fault / Repeated Limit Trips

9 FLASH

Furnace will not start; LED flashes nine times repeatedly; no inducer or blower response to thermostat.

Line Voltage Polarity or Ground Fault

CODE 11

LED flashes one short and one long blink; furnace fails to ignite after several attempts.

Ignition Lockout Due to Recycle Limit

CODE 12

LED flashes one short and two long blinks; furnace lights but shuts down intermittently.

Flame Sense Low or Intermittent

CODE 13

LED flashes one short and three long blinks; blower runs but burners do not light.

Limit Circuit Lockout

CODE 21

LED flashes two short and one long blink; inducer runs but burners do not light.

Gas Heating Lockout

CODE 22

LED flashes two short and two long blinks; blower runs at low speed; no heat.

Blower Fault or Lockout

CODE 31

LED flashes three short and one long blink; inducer does not start; no ignition.

Pressure Switch Open or Inducer Fault

CODE 32

LED flashes three short and two long blinks; furnace cycles on and off frequently; may not reach set temperature.

Low Heat Pressure Switch Fault

CODE 41

LED flashes four short and one long blink; blower runs at incorrect speed or not at all.

Blower Motor Fault (ECM or PSC)

CODE 42

LED flashes four short and two long blinks; inducer runs continuously; no ignition.

Inducer or Pressure Switch Stuck Closed

CODE 44

LED flashes four short and four long blinks; furnace shuts down unexpectedly during operation.

Secondary Limit or Condensate Switch Open

CODE 45

LED flashes four short and five long blinks; furnace locked out; no heating cycles.

Control Board Lockout Due to Multiple Faults

NO LED

No LED light on control board; furnace completely dead; no blower or inducer operation.

No Power to Furnace or Failed Control Board

STEADY ON

LED on control board is solid on with no flashing; furnace does not respond to thermostat.

Control Board Powered, No Call for Heat or Internal Board Fault

Symptom

Furnace blower runs continuously even when thermostat is not calling for heat.

Continuous Fan Operation

Symptom

Furnace burners light but one or more burners do not cross‑light properly, causing uneven flame.

Poor Cross Ignition Between Burners

Symptom

Furnace cabinet vibrates excessively and rattles during blower operation.

Mechanical Vibration or Imbalance

Symptom

Furnace cycles on and off rapidly (every few minutes) with noticeable clicking from the thermostat.

Thermostat or Control Anticipator Issue

Symptom

Furnace ignites but shuts down after a minute or two; blower continues to run with cool air.

High Limit Trip Due to Restricted Airflow

Symptom

Furnace ignitor does not glow; inducer runs and pressure switch closes but no ignition.

Hot Surface Ignitor Failure

Symptom

Furnace is very loud with rumbling or roaring noise during operation.

Combustion or Duct Resonance Noise

Symptom

Furnace makes loud banging or booming noise at startup.

Delayed Ignition

Symptom

Furnace occasionally fails to start on very cold or very windy days.

Marginal Venting or Pressure Switch Sensitivity

Symptom

Furnace occasionally trips the household circuit breaker.

Electrical Overload or Short Circuit

Symptom

Furnace produces a high‑pitched whine or screeching noise during operation.

Blower or Inducer Bearing Wear

Symptom

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

Combustion or Venting Safety Hazard

Symptom

Furnace runs but does not keep the house warm; short cycles on and off frequently without reaching set temperature.

Short Cycling Due to Overheating or Oversizing

Symptom

Furnace runs but some rooms are cold; weak airflow from certain registers.

Insufficient Airflow or Duct Restriction

Symptom

Furnace starts and stops with a loud click but blower never comes on; heat exchanger gets very hot.

Blower Motor Not Starting

Symptom

Furnace starts but shuts off after a few seconds; burners light then go out repeatedly.

Flame Sensing Failure

Symptom

Furnace will not start at all; thermostat shows a call for heat but nothing happens.

No Call Reaching Control Board

Symptom

Strong burning or electrical smell when the furnace runs.

Overheating Components or Dust Burn‑Off

Symptom

Water leaking around the base of the furnace or onto the floor during heating.

Condensate Leak