HVACopediaMitsubishi · Heat pump
P5 Drain overflow - float switch wet with pump running
What the control is telling you
The float switch has been under water for 90 seconds with the drain pump on. The compressor and indoor fan stop; if it happens again the unit locks out with P5.
Applies to: PEAD-RP35/50/60/71/100/125/140JA and JA(L) ducted indoor units (220-240 V models)
Likely causes
- Drain pump not working
- Drain pump or condensate line clogged
- Float switch stuck in the up (wet) position
- Faulty indoor control board
Test and repair steps
- Turn the unit off at the remote first, then switch off the breaker before opening the unit or unplugging connectors.
- Check the condensate pan and drain line; clear any clog, slime or blockage.
- Pour water into the pan and confirm the drain pump runs and pushes the water out.
- Unplug the float at CN4F and check it closed with the float up, open with the float down. Closed with the float down = replace the float switch.
- If the float is good and P5 returns with CN4F reading correctly, replace the indoor board.
- If none of the above is wrong, cycle power and run the unit.
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Mitsubishi Electric PEAD-RP35-140JA(L) Service Manual, 10-3 Self-diagnosis action table, p.31. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.