Google Nest Cooling Call Signal Not Reaching Condenser

Nest thermostat calls for cooling but AC does not turn on

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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 Y1 wire at Nest base, Broken Y1 conductor, Blown low-voltage fuse due to short at condenser, Failed contactor coil in outdoor unit

How to Fix / Troubleshooting

Safety warning: Turn off power to both indoor and outdoor units before working on wiring.

  • Verify Nest cooling call: Set the thermostat to cool and lower the setpoint below room temperature. Confirm it shows cooling.
  • Inspect Y1 wiring: Check that the Y1 wire is secure at the Nest base and at the furnace/air handler Y terminal.
  • Check outdoor unit low-voltage wires: Open the condenser control panel and ensure the two low-voltage wires from the furnace (usually Y and C) are intact and not corroded or chewed by rodents.
  • Inspect control board fuse: If the furnace control board fuse is blown, replace it after correcting any shorts at the condenser.

If the contactor does not pull in when Y is energized, the contactor coil or outdoor control board may be defective and should be tested by an HVAC technician.

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Repair Difficulty

Hard 4/5

Required Part

Nest Thermostat Base (Y1 terminal), Outdoor Condenser Contactor
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