Lennox HVAC Error Code 204

Error code 204 on a Lennox air handler means the blower motor failed to start during a run cycle. The control board detected no motor operation within the required startup window and placed the system into watchguard mode to prevent damage. The fault points to a mechanical or electrical problem with the blower motor or blower wheel assembly.

No. When code 204 is active, the system enters watchguard mode and will not run the blower, meaning conditioned air cannot circulate through your home. Attempting to force operation without resolving the underlying fault risks overheating the motor and causing further damage to the air handler's electrical components.

Repair costs vary depending on the cause. Clearing a simple obstruction from the blower wheel may cost only a service call fee, typically in the range of $75 to $150. Replacing a blower motor or wheel assembly is more involved and parts plus labor can range from $300 to $800 or more depending on the specific unit and local labor rates.

A knowledgeable DIYer can safely disconnect power and visually inspect the blower wheel for obstructions or debris, which sometimes resolves the issue without parts. However, diagnosing a seized bearing, failed motor, or control board fault involves working near live electrical components and requires proper tools and experience. Motor replacement in particular is best handled by a qualified HVAC technician.

Resetting the system will clear the watchguard lockout temporarily, but if the underlying cause of the blower not starting has not been corrected, the fault will return immediately or within the next startup attempt. The reset should only be performed after the mechanical or electrical problem has been identified and repaired.