Lennox Heat Pump Error Code 15

Error code 15 on a Lennox heat pump means the mode jumper on the TSC-6 control board is not properly in place. The TSC-6 requires a physical jumper to be seated across the correct set of pins to identify the operating mode. Without this, the control board cannot function properly and the system will not operate. This is a configuration issue, not a mechanical or refrigerant problem.

When error code 15 is active, the TSC-6 control board cannot determine the correct operating mode, which means the system will likely not run or will operate unreliably. Continuing to attempt operation in this state is not recommended. The fix is straightforward and should be addressed before using the system to avoid any secondary issues.

Resetting the system will not permanently clear error code 15 because the underlying cause, a missing or improperly seated jumper on the TSC-6, is a physical hardware condition. The error will return any time the control board checks for the jumper and does not detect it. The jumper must be physically inspected, correctly seated, and confirmed to be on the right set of pins before the error will clear and stay clear.

To fix error code 15, locate the TSC-6 control board inside the unit and find the jumper pins. Check whether the jumper is present, fully seated, and positioned across the correct pair of pins for your system's operating mode. If the jumper is loose, press it firmly into place. If it is missing entirely, a replacement jumper must be installed on the correct pins before the system will clear the fault.

If the jumper is simply loose or misplaced, the cost is limited to the service call fee, which typically ranges from $75 to $150 depending on your area. If the jumper itself needs to be replaced, the part cost is minimal, usually just a few dollars for a standard pin jumper. Labor for this type of diagnostic and repair is generally on the lower end since it is a quick fix.