Google Nest Cooling System Misconfiguration or Low Refrigerant (HVAC-side)

Nest thermostat shows cooling is on, but air from vents is warm or not cold enough

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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

Heat pump reversing valve set incorrectly, Outdoor unit not running while indoor blower runs, Low refrigerant charge, Dirty condenser or evaporator coil

How to Fix / Troubleshooting

Safety warning: Turn off power before opening any HVAC panels. Refrigerant work must be done by a licensed technician.

  • Confirm outdoor unit operation: When Nest calls for cooling, verify the outdoor condenser runs and the fan spins.
  • Check Nest heat pump settings: Ensure the O/B setting matches the manufacturer's requirement so that the reversing valve is in cooling mode when needed.
  • Clean filters and coils: Replace or clean the air filter. Visually inspect the outdoor coil for debris and gently rinse with a garden hose (power off).

If the system still does not cool adequately, a professional should check refrigerant levels, superheat/subcooling, and overall system performance.

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Repair Difficulty

Hard 4/5

Required Part

Outdoor Condenser Unit, Heat Pump Reversing Valve
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