TP-Link Kasa
No Cooling Call Output or Open Y Circuit
Thermostat calls for cooling but the AC does not start.
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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 or broken Y wire, blown fuse on furnace or air handler board, failed Y output relay on thermostat, miswired outdoor unit low-voltage connections.
How to Fix / Troubleshooting
Safety: Turn off power to indoor and outdoor units before working on wiring.
- Confirm call for cool: Set the thermostat to Cool and lower the setpoint. Verify the thermostat indicates a cooling call.
- Check Y wiring: At the thermostat and furnace/air handler board, ensure the Y conductor is secure and not corroded.
- Outdoor unit wiring: At the condenser, inspect the low-voltage connections from the furnace/air handler. Tighten any loose wire nuts or terminal screws.
- Fuse check: Inspect the low-voltage fuse on the furnace/air handler board and replace if blown after checking for shorts.
- Technician test: A technician can jumper R to Y at the furnace board to see if the outdoor unit starts. If it does, but not via the thermostat, replace the thermostat.
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Repair Difficulty
Hard
4/5
Required Part
Cooling Call (Y) Circuit / Thermostat Relay
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