P4
Fraser-Johnston Indoor Fan Motor / DC Motor Protection in Inverter System

P4 error, indoor unit stops and may flash LEDs

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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

Locked indoor fan motor, Failed DC fan driver on indoor PCB, Loose fan harness, Obstructed blower wheel

How to Fix / Troubleshooting

Safety: Turn off indoor unit power at the breaker.

  • Check blower wheel: Access the blower and ensure it spins freely. Remove any obstructions.
  • Inspect wiring: Reseat the DC fan motor connector on the indoor PCB.
  • Test motor: With power restored, command fan ON. If the motor does not start and correct DC voltage is present, replace the indoor DC fan motor.
  • PCB driver: If a new motor does not resolve P4, the indoor PCB fan driver circuit may be defective.
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Repair Difficulty

Medium 3/5

Required Part

Indoor DC Fan Motor
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