Furnace runs but shuts off after a few minutes, then restarts; home never reaches set temperature.

Safety: Turn off power before accessing blower compartment.

Steps:

• Replace filter: Install a new filter of the correct size and MERV rating. Avoid overly restrictive filters unless the duct system is designed for them.
• Open registers: Ensure all supply and return registers are open and unblocked.
• Check blower operation: Observe the blower motor during a heat call. If it starts slowly, overheats, or stops intermittently, the motor or capacitor may be failing.
• Blower speed tap: On PSC motor models, verify that the heating speed tap on the Concord control board is set appropriately (this is typically a technician task).

Note: Persistent limit cycling can damage the heat exchanger; have a technician evaluate airflow and blower performance.