F3
York
Outdoor Unit Demand / Y Circuit Fault
York furnace/air handler board flashes F3 and outdoor unit does 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 Y call between thermostat and outdoor contactor, Broken wire to outdoor unit, Failed contactor coil, Faulty control board Y output
How to Fix / Troubleshooting
Safety: Turn off power to both indoor and outdoor units before handling wiring.
- Check Y circuit continuity: With power off, use a multimeter to check continuity from the Y terminal at the indoor control board to the contactor coil at the York outdoor unit. Repair any open wires.
- Inspect contactor coil: Measure resistance across the contactor coil. An open reading indicates a failed coil; replace the contactor.
- Verify thermostat call: Ensure the thermostat is calling for cooling and sending 24V between R and Y.
- Test board output: If wiring and contactor are good but no 24V appears on Y when cooling is called, the indoor control board may be faulty and require replacement.
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Repair Difficulty
Hard
4/5
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