P4 error on Certikin heat pump; unit shuts down unexpectedly.

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

Failed ambient sensor, Sensor not located in free air, Cable damage from UV or weather, Faulty connection to control PCB

Safety first: Isolate power before accessing outdoor sensors.

Locate ambient sensor: Find the air temperature sensor, usually clipped near the evaporator coil or in the air stream.
Check position: Ensure it is not touching hot surfaces or enclosed where air cannot circulate.
Inspect cable: Look for weather damage, UV cracking, or rodent damage.
Reconnect: Reseat the sensor connector on the control board.
Restart: Restore power and observe if P4 clears.

If the error persists, replace the ambient sensor with a Certikin-approved part.

Medium 3/5

Certikin heat pump ambient air temperature sensor

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