Ruud
Stuck Contactor or Thermostat Control Fault
Ruud air conditioner outdoor unit runs in cold weather when it should be off (for straight cool systems).
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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
Welded contactor contacts, Shorted thermostat wiring calling for cooling, Miswired thermostat (heat pump vs AC mode), Faulty control board relay
How to Fix / Troubleshooting
Safety first: Turn off power at the outdoor disconnect and indoor breaker before inspecting contactor or wiring.
- Step 1 – Verify thermostat mode: Ensure thermostat is set to OFF or HEAT only for straight cool systems in winter.
- Step 2 – Inspect contactor: With power off, check if the Ruud contactor contacts are stuck closed. If the plunger is down and cannot move freely, replace the contactor.
- Step 3 – Check thermostat wiring: Look for shorts between Y and R wires at the thermostat, air handler, and outdoor unit.
- Step 4 – Control board relay: If the board is energizing the contactor without a call for cooling, the board relay may be stuck and the board should be replaced.
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Repair Difficulty
Medium
3/5
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