HF35 / HF36 — Micro-Electronic Component Failure (Fatal)

What does HF35 / HF36 mean?

These are Fatal Hardware Failure (HF) errors indicating a critical internal micro-electronic component failure within the slave thermostat. When either of these errors occurs, the slave thermostat completely loses its ability to control the zone.

• Internal electronic component malfunction within the slave thermostat.
• A severe internal defect or damage to the slave thermostat's circuit board.

Click steps to track your progress.

1. 1

   Verify that the slave thermostat is receiving stable and correct power supply voltage.

2. 2

   Carefully inspect the slave thermostat for any visible signs of damage or loose internal components, if safely accessible.

3. 3

   Since these are fatal errors, the slave thermostat itself is likely defective and requires replacement.

4. 4

   Contact a qualified HVAC technician for diagnosis and replacement of the unit.