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Grant Aerona R32 fault C7

Controller PCB serial error

Heat pump

What it means

Serial communication error between Main PCB and Controller PCB, potentially due to mis-wiring, loose contact, Controller PCB fault, Main PCB fault, or earth wire fault.

Likely causes

  1. Mis wiring or rare contact of Main PCB - Controller PCB connecting cable
  2. Controller PCB fault
  3. Main PCB fault

Where to start

  1. Check the wiring connection and rare contact
  2. Confirm pre-plumbed cylinder wiring already completed if applicable
  3. Check shielding used if cable run exceeds 30m for wiring centre to heat pump cable

The full answer, free

  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 56), right under the answer
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Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.

From the Grant manual for the Aerona R32. Check the model on the data plate before you order parts.

Other Grant Aerona R32 fault codes