What This Error Means

Error code 22 indicates that the main limit or high-temperature safety circuit is open. The furnace shuts off the burners to protect the heat exchanger from overheating.

Symptoms You May Notice

Furnace starts but shuts off before reaching the thermostat setting; indoor blower may continue running; short heating cycles; weak airflow; repeated restart attempts; code 22 displayed.

Common Causes

Dirty air filter; closed or blocked supply registers; restricted return airflow; dirty evaporator coil; blower motor or capacitor problem; loose blower wheel; incorrect blower speed; failing limit switch; less commonly, a control-board issue.

Safe Troubleshooting Steps

1. Turn off furnace power before opening any panel. 2. Replace a dirty air filter with the correct size and rating. 3. Confirm supply registers and return grilles are open and unobstructed. 4. Restore power and confirm the blower starts and produces steady airflow. 5. Allow the furnace to cool before one restart attempt. 6. If code 22 returns, stop resetting the furnace and arrange professional service. 7. A technician should measure temperature rise, airflow, blower performance, and limit-switch operation.

Parts Commonly Involved

Main limit switch; blower motor; blower capacitor; blower wheel; air filter; duct system; evaporator coil; integrated furnace control.

When to Call a Technician

Call a technician if code 22 returns after replacing the filter and opening vents, if airflow is weak, or if the blower does not operate normally.

Safety Notice

Never bypass or jumper a limit switch. It is a critical safety device that protects the furnace and heat exchanger from excessive temperature.

Manufacturer Documentation