Keystone air conditioner shows F2 and may cycle erratically or shut down.

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.

Possible Causes

Evaporator thermistor drifted out of range, poor thermal contact with coil, damaged harness, faulty control board

Safety: Disconnect power before opening the unit.

Steps:

Check sensor mounting: Confirm the evaporator sensor is firmly attached to the coil tubing with good contact. Use aluminum tape if necessary to improve contact.
Inspect for icing: Look for signs of frequent icing that could stress the sensor. Clean filter and coil to improve airflow.
Test sensor: Measure resistance and compare to spec. Replace if significantly off.
Replace board if needed: If a correct sensor still results in F2, the main PCB may be misreading and should be replaced.

Medium 3/5

Evaporator Temperature Sensor

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