HVACopedia

Mitsubishi · Heat pump

P6 Coil freeze or overheat protection

High severity Mr. Slim PEAD-RP JA(L) ducted indoor unit

What the control is telling you

Cooling: the indoor coil stayed below -15°C for 3 minutes after the compressor started, twice within 16 minutes. Heating: the coil went above 70°C, twice within 10 minutes. The unit pauses 6 minutes after the first event and locks out with P6 on the second.

Applies to: PEAD-RP35/50/60/71/100/125/140JA and JA(L) ducted indoor units (220-240 V models)

Likely causes

  • Dirty filter or low airflow
  • Supply air short-cycling back to the return
  • Running outside the allowed temperature range (very cold in cooling, very hot in heating)
  • Indoor fan motor or its board drive faulty
  • Outdoor fan not controlled properly
  • Refrigerant overcharge
  • Restriction in the refrigerant circuit
  • Heating only: outdoor unit bypass circuit faulty

Test and repair steps

  1. Check and clean or replace the filter and look for closed or blocked registers.
  2. Look for supply air being drawn straight back into the return and remove the cause.
  3. Confirm the indoor fan runs at the right speed (see the DC fan motor check in the manual, section 10-8).
  4. Check that the outdoor fan runs.
  5. Check the refrigerant charge and look for restrictions with gauges.
  6. After the repair, cycle the power and run the unit to confirm the code does not come back.

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.

Open the app

Source: Mitsubishi Electric PEAD-RP35-140JA(L) Service Manual, 10-3 Self-diagnosis action table, p.32. 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.