E12
ACV Communication Error Between Control Board and User Interface

Boiler shows E12, no ignition, often after wiring changes or surge

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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.

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Possible Causes

Loose communication cable, Faulty display board, Faulty main PCB, Electrical interference

How to Fix / Troubleshooting

Safety first: Isolate power before accessing internal wiring.

  • Power reset: Turn off the boiler at the main isolator for at least 1 minute, then restore power.
  • Check external controls: If an ACV-provided room controller or cascade controller is connected, ensure its cables are intact and firmly connected.
  • Visual inspection: A competent person can check the low-voltage communication harness between the main PCB and the front display board for loose plugs or damage.
  • Professional repair: If E12 persists, a technician may need to replace the display board, main PCB, or both, and update any ACV-specific parameters.
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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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