21
Immergas
Communication Fault with Remote Controller / Bus
Display shows 21, boiler may lock out randomly, sometimes after thermostat or bus wiring changes
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Incorrect bus wiring polarity, Broken bus cable, Incompatible or faulty Immergas controller
How to Fix / Troubleshooting
Safety: Turn off power before altering control wiring.
Steps:
- 1. Check controller type: Ensure you are using a compatible Immergas controller (e.g., CARV2, Super CAR) for your model.
- 2. Inspect bus wiring: Verify that the two bus wires are connected to the correct terminals and maintain polarity from boiler to controller. Avoid mixing with mains cables.
- 3. Cable integrity: Look for damage, joints, or moisture along the cable route. Replace if suspect.
- 4. Test with simple link: Temporarily disconnect the bus controller and fit the factory jumper (if required) to see if the boiler operates normally.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Immergas Remote Controller (CAR / CARV2)
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements