Trane communicating furnace control displays 'Err 1' on the ComfortLink II or communicating thermostat
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power to the indoor unit before working on low-voltage wiring.
Steps to check:
- Inspect ABCD wiring: At both the thermostat and furnace, verify that the ABCD terminals are wired color-for-color and in the same order. Loose or crossed wires can cause Err 1.
- Check cable condition: Look for staples through the cable, crushed sections, or water damage.
- Power cycle: Turn off power to the furnace and thermostat for 1 minute, then restore to reset communication.
When to call a professional: If wiring is correct and Err 1 persists, a Trane dealer should test the communicating thermostat and furnace control board and replace as needed.
Repair Difficulty
Required Part
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