Lennox Furnace Error Code E307

E307 on a Lennox furnace means the LSOM has detected that the compressor contactor is welded, meaning its internal contacts are stuck in the closed position and cannot open to shut off the compressor. This is a critical fault because it prevents the system from properly controlling compressor operation. The contactor must be inspected and replaced to resolve the error.

No, continuing to operate the system with a welded contactor is not safe. A stuck-closed contactor allows the compressor to run continuously without proper cycling, which can lead to compressor overheating, refrigerant pressure problems, and eventual compressor failure. The system should be shut down until the contactor is replaced.

Contactor replacement is generally a straightforward repair. Parts costs for a replacement contactor typically range from $15 to $75 depending on the specific unit requirements, and labor costs from an HVAC technician can range from $75 to $200 or more depending on your region and service provider. Total repair costs usually fall in the range of $100 to $300 in most cases.

Replacing a compressor contactor involves working with high-voltage components in the outdoor unit, which requires disconnecting power safely and handling wiring. While a knowledgeable DIYer with electrical experience may be able to perform the swap, most homeowners should call a licensed HVAC technician. Mishandling the repair can create shock hazards or cause additional component damage.

Resetting the system may temporarily clear the fault display, but the underlying hardware problem, the welded contactor, will still be present. The E307 code will return once the control module checks the contactor's state again. A reset is not a fix and should not be relied upon as a solution.