Mitsubishi Electric P8

What does Mitsubishi Electric P8 mean?

The indoor unit reported a pipe temperature error, shown as P8 on the wired controller. The pipe thermistor monitors the indoor coil's refrigerant pipe temperature; when that temperature is outside the expected range for the operating mode, this code is set. It can reflect a sensor or wiring fault, restricted airflow, or a refrigerant-side condition affecting coil temperature.

Symptoms

• P8 displayed on the wired controller
• Indoor unit stops or fails to maintain temperature
• Coil noticeably too cold or too warm for the mode
• Code recurs after restart

Common causes

• Pipe thermistor disconnected, open, or shorted
• Restricted airflow over the indoor coil
• Refrigerant charge problem
• Pipe sensor mounted poorly or wiring damaged

Diagnostic steps

1. 01

   Power down the indoor unit

   Switch off power before inspecting the indoor unit.

2. 02

   Restore airflow

   Clean or replace the filter and clear the indoor coil and grilles.

3. 03

   Check the pipe sensor

   Verify the pipe thermistor is seated against the pipe and its connector is secure.

4. 04

   Inspect the wiring

   Look for damaged or pinched sensor wiring that could open or short the circuit.

5. 05

   Restart and confirm

   Restore power and check whether P8 clears after airflow and the sensor are addressed.

When to call a professional

Call a technician if P8 persists after airflow is restored and the sensor connector is checked, since confirming a thermistor fault requires resistance testing and a refrigerant-side cause requires gauges. Both need service tools and certification. A qualified professional should verify the pipe sensor and the charge before extended operation.