Furnace error code, most common

Primary/secondary limit switch open

LED 1 Slow flash, LED 2 On

System Overheat, Check your filter ,Test the blower motor operation mode (Fan On)

Medium Efficiency Furnace

Low/High pressure switch

E223,E 224, E225, E226

Pressure switch failed to open or close (Vents blocked, Condensation circuit blocked, Draft motor not operate)

98% Efficiency furnace


LED 1 Alternating Slow-Flashing, LED 2 Alternating Slow-Flashing

Burners not ignite ( No gas, igniter broken) lost flame sense 5 times (clean flame sensor)

Medium Efficiency Furnace

Soft Lockout


No flame current sensed (No gas, igniter broken, low flame signal)

98% Efficiency furnace

Carrier error code

Most common Carrier furnace error code

Pressure switch did not close or reopen

LED code 31 

Defective inducer motor, defective pressure switch, Restricted vent


Blower on after power up

Blower runs for 90 sec if unit is powered up during a call for heat


Limit circuit fault

LED code 33

Dirty filter, Defective blower motor or capacitor, Inadequate combustion air supply.


Ignition proving failure

LED code 34

Lost flame signal or no flame sensor signal. ( no gas pressure or no presence of flame at burners)