Lennox HVAC Error Code 352

Error code 352 on a Lennox air handler indicates that the second stage electric heat pilot relay did not respond correctly. Either the relay coil failed to energize or its contacts did not close when the system called for second stage heat. The system will continue operating on first stage heat only until the fault is resolved. The code clears automatically once the relay is detected functioning correctly.

Yes, it is generally safe to continue using the system with error 352 active, as the air handler is designed to fall back to first stage heat operation rather than shutting down entirely. Your home will still receive some heat, though capacity will be reduced. The underlying relay fault should still be repaired promptly to restore full heating output and prevent additional strain on the first stage components.

A simple reset will not permanently clear error 352. The fault is condition-based, meaning the code clears only when the control board actually detects that the second stage relay has successfully closed. If the underlying problem with the relay coil, contacts, or wiring is not corrected, the fault will return as soon as the system calls for second stage heat again.

Some basic checks, such as inspecting wiring connections and verifying terminal tightness, can be done by a knowledgeable homeowner. However, diagnosing relay coil resistance, measuring live voltages at the relay terminals, and replacing components inside an air handler involves working near high-voltage electric heating circuits, which requires appropriate safety precautions and experience. A licensed HVAC technician is recommended for anything beyond visual inspection.

Repair costs depend on the root cause. If only a wiring connection needs to be corrected, the cost may be limited to a service call fee, typically in the range of $75 to $150. Replacing the second stage relay itself usually adds $50 to $200 in parts depending on the specific component. If the control board is the source of the fault, board replacement can range from $200 to $600 or more including labor.