P4
Carrier
Inverter Module Overheating / IPM Temperature Protection
Indoor unit shows P4 and system may not run or may shut down under heavy load
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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
Blocked airflow around outdoor control box, Failed control box cooling fan (if equipped), Poor heat sink contact, High ambient temperature combined with heavy load
How to Fix / Troubleshooting
Safety: Turn OFF power at the disconnect and breaker.
- Step 1 – Inspect control box: Open the outdoor control panel and check for dust buildup on heat sinks and components. Gently blow out dust with dry compressed air.
- Step 2 – Check cooling fan: If the control box has a small fan, ensure it runs when the system is operating. Replace if not running.
- Step 3 – Improve ventilation: Ensure the outdoor unit is not installed in a confined, unventilated space.
- Step 4 – Technician service: Persistent P4 may require replacement of the inverter module or outdoor PCB by a Carrier technician.
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Repair Difficulty
Hard
4/5
Required Part
Outdoor Control Box Cooling Fan
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