Errors 83-87 — Communication problem between boiler board and control unit

What does 83-84-85-86-87 mean?

A range of error codes from 83 to 87 signifies a communication issue between the boiler's main board and the external control unit (like a Baxi modulating room unit). This prevents the boiler and control from interacting correctly.

• Loose or incorrect wiring connection between the control unit and the M2 bus terminal.
• Short circuit in the wiring connecting the control unit.
• Faulty boiler board or control unit.

Click steps to track your progress.

1. 1

   Check the wiring connection between the Baxi modulating room unit and the M2 bus terminal position 1 & 2 for secure contact.

2. 2

   Inspect the wiring for any signs of a short circuit along its length.

3. 3

   If connections and wiring are sound, a professional technician may need to diagnose the boiler board or control unit.