Code 78 — High stage didn’t start three times

What does 78 mean?

The system's high stage compressor has failed to start successfully after three attempts. This indicates a problem preventing high-stage operation.

• High stage compressor failure
• Wiring issue to the high stage compressor
• Electrical fault
• Overheating preventing start

Click steps to track your progress.

1. 1

   Check wiring connections to the high stage compressor.

2. 2

   Verify electrical supply to the high stage compressor.

3. 3

   Inspect for any signs of overheating.

4. 4

   Contact an HVAC technician for compressor diagnosis.