Error 78 (7 Green, 8 Red Flashes) — Expansion valve thermistor error

What does 78 mean?

The hydraulic unit's green LED flashes seven times and the red LED flashes eight times. This indicates an issue with the thermistor associated with the expansion valve.

• Faulty expansion valve thermistor.
• Loose or damaged wiring to the thermistor.
• Problems with refrigerant flow affecting thermistor readings.

Click steps to track your progress.

1. 1

   Perform a full power reset of the heat pump system by turning off the main breaker for 60 seconds and then turning it back on.

2. 2

   Ensure the outdoor unit is not obstructed, allowing proper airflow.

3. 3

   If the error persists, contact a qualified technician, as issues with the expansion valve or its thermistor often require specialized refrigerant handling and diagnostic tools.