Lennox Heat Pump Error Code DS2 OFF / DS1 OFF

This error indicates that the control board is not receiving 24VAC power at its R and C control terminals. Both diagnostic LEDs go dark because the board has no power to operate them. The cause is either a loss of 24VAC from the control transformer or a complete failure of the control board itself. A technician will check for voltage at those terminals to determine which component is at fault.

The unit will not operate at all when this error is active because the control board has no power. There is no immediate safety hazard from the error itself, but do not attempt to bypass the control circuit to force operation. If the underlying cause is a short circuit or wiring fault, operating the system without correcting it could create a fire risk or cause further component damage.

A simple reset will not clear this error because the control board has no power to process a reset command. The underlying power supply issue must be corrected before the board can initialize and restore normal operation. Once the transformer, fuse, wiring, or board is repaired or replaced and 24VAC is restored to the R and C terminals, the system should power up and resume normal diagnostics automatically.

Start by measuring voltage at the R and C terminals on the control board using a multimeter; you should see approximately 24VAC. If voltage is absent, inspect the control transformer, any low-voltage fuses, and the wiring between the transformer and the board. If 24VAC is present at the terminals but the board still shows no signs of life, the control board has failed and needs to be replaced.

Repair cost depends on the root cause. Replacing a blown low-voltage fuse is typically inexpensive, often under $50 including a service call. A failed control transformer replacement generally ranges from $150 to $350 depending on the model. If the control board itself has failed, parts and labor can range from $400 to $900 or more depending on the specific board and local labor rates.