Bryant Communicating Control Network Fault

Bryant communicating furnace displays communication error with thermostat; furnace may revert to default operation or not run.

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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

Open or shorted ABCD communication wiring, incorrect polarity on ABCD terminals, incompatible thermostat, failed communicating control board

How to Fix / Troubleshooting

Safety first: Turn off power to both furnace and thermostat before changing ABCD wiring.

  • Verify wiring: At both furnace and Bryant Evolution/Connex thermostat, ensure ABCD terminals match color-for-color and polarity (A to A, B to B, etc.).
  • Check cable: Inspect the communication cable for staples through the jacket, kinks, or water damage.
  • Reset system: After correcting wiring, power up the furnace first, then the thermostat, and allow the system to re-detect equipment.

If communication errors persist with correct wiring, the communicating control board or thermostat may need replacement.

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Repair Difficulty

Hard 4/5

Required Part

Communicating Control Board
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