Error 77 (7 Green, 7 Red Flashes) — Outdoor unit heat sink temp. thermistor error

What does 77 mean?

The hydraulic unit's green LED flashes seven times and the red LED flashes seven times. This indicates an error with the thermistor monitoring the temperature of the heat sink in the outdoor unit.

• Faulty heat sink temperature thermistor.
• Poor contact between the thermistor and the heat sink.
• Overheating of the heat sink due to inadequate cooling or heavy load.

Click steps to track your progress.

1. 1

   Turn off the heat pump system at the main breaker, wait one minute, then switch it back on.

2. 2

   Ensure the outdoor unit is clear of any obstructions that could impede airflow and cooling.

3. 3

   Check for excessive dirt or dust accumulation on the heat sink fins and clean them if necessary (with power off).

4. 4

   If the error persists, contact a qualified technician to diagnose or replace the heat sink thermistor.