Display shows 09, furnace does not respond to room thermostat or external controls

Safety: Isolate power before working on control wiring.

Steps:

• 1. Check thermostat settings: Ensure the room thermostat or Immergas remote control is calling for heat and batteries (if any) are good.
• 2. Inspect wiring: At the boiler terminal strip, verify that the thermostat wires are correctly connected to the designated terminals (e.g., TA, COM). Look for loose strands or shorts.
• 3. Bypass test (technician or skilled DIY): With power off, temporarily fit a jumper wire across the room thermostat terminals. Restore power; if the boiler now responds, the thermostat or its wiring is faulty.
• 4. External control modules: If using an Immergas proprietary controller (e.g., CARV2, Super CAR), check the bus connection and polarity. Replace the controller or cable if defective.