- HVAC
- Air conditioner
P6
Mitsubishi Electric P6 air conditioner: freeze or overheat stop
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Mr. Slim PKA splits, P6 means the indoor coil's freezing protection (cooling) or overheating protection (heating) has tripped. Switch off at the breaker, clean the filter as the user manual describes and clear anything blocking the air inlet or outlet.
Safety first
Stop and check this first
- Turn off the breaker before cleaning the filter or grille. Mitsubishi Electric requires the supply to be disconnected before accessing terminals: do not open the indoor casing or the outdoor unit panels.
- Do not adjust the refrigerant charge or touch the service valves: the manual requires R410A-specific tools and refrigerant recovery, which only a certified technician can do.
Safe checks you can perform
- Confirm the code and the mode
- Clean the filter with the power off
- Clear obstacles around both units
- Fans and refrigerant circuit
Leave these tasks to a qualified professional
- Do not attempt this professional task: Indoor fan motor test
- Do not attempt this professional task: Outdoor fan check
- Do not attempt this professional task: R410A circuit check
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Indoor fan motor test
What they doThe technician tests the indoor fan motor and board with Mitsubishi Electric's procedure.
They must show youthe motor test and its result.
In writingcode P6, the mode it appeared in, the test result and any part replaced with the reason.
Outdoor fan check
What they doThey check that the outdoor unit fan runs and that its control responds.
They must show youthe outdoor fan running and the check of its control.
In writingcheck result and repair made.
R410A circuit check
What they doThey measure pressures and temperatures in the mode where P6 appeared to rule out overcharge or clogs.
They must show youthe pressures and temperatures measured in the relevant mode.
In writingreadings, leak test result and kg of R410A recovered or charged if the charge was changed.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Confirm the code and the mode
- Who:
- you, with the unit's remote.
- How:
- read the code with the remote's check method (CHECK twice, TEMP for the address and HOUR pointed at the unit, as Mitsubishi Electric describes). P6 is 6 blinks of the operation lamp. Note whether it was in cooling, dry or heating.
- Result that matters:
- knowing whether the freezing protection (cooling or dry) or the overheating protection (heating) tripped.
- If you see P6:
- note the mode and rough outdoor temperature and continue with the next steps.
- If you see P8 or another code:
- check its own page, because the manual treats them separately.
- Evidence to keep:
- a photo of the code, the mode, the set temperature and the time.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Clean the filter with the power off
- Who:
- you.
- How:
- switch off with the remote and turn off the breaker. Remove and clean the filter as your unit's user manual describes, let it dry and refit it before restoring power. Do not open anything beyond the grille the user manual shows.
- Result that matters:
- air passing freely through the filter, the first cause Mitsubishi Electric lists.
- If the filter was very dirty and P6 does not return:
- keep up regular cleaning.
- If the filter was clean or P6 returns:
- continue with the next step and call a technician.
- Evidence to keep:
- photos of the filter before and after and the cleaning date.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Clear obstacles around both units
- Who:
- you, without opening either unit.
- How:
- check that no furniture, curtains or objects block the indoor unit's air inlet or outlet, and that no plants, boxes or covers surround the outdoor unit. The manual says to remove obstacles that make the air short cycle.
- Result that matters:
- air entering and leaving both units freely.
- If something was blocking:
- remove it, do a single reset from the breaker and watch whether P6 returns.
- If everything was clear:
- the cause may be a fan or the refrigerant circuit; call a technician.
- Evidence to keep:
- photos of the area around each unit.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Fans and refrigerant circuit
- Who:
- an F-gas certified air conditioning technician.
- How:
- checks the indoor fan motor with the manual's procedure, inspects the outdoor fan and checks the refrigerant circuit operating condition (pressures and temperatures in the relevant mode).
- Result that matters:
- whether P6 comes from a fan, the board or the R410A circuit (overcharge or clog).
- If a fan or the board fails:
- the indicated part is replaced.
- If pressures or temperatures are abnormal:
- the charge and circuit clogs are checked.
- Evidence to keep:
- motor test result and the pressures and temperatures measured.
Involves electrical parts inside the units and a high-pressure R410A circuit: certified technician only.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Mitsubishi Electric
- Product type
- Air conditioner
Known code variants
- Mitsubishi Electric P6
- Mitsubishi P6
- Mr. Slim P6
- PKA P6
What it means
In service manual OCH639 for the PKA-A24/30/36KA7 indoor units, Mitsubishi Electric links P6 to freezing or overheating protection: in cooling it trips if the pipe stays below -15 °C for 3 minutes and it repeats after the 6-minute restart delay; in heating, if it exceeds 70 °C and repeats within 30 minutes. Other models may behave differently. The code alone never proves that a specific part is faulty: often the cause is poor airflow.
Warnings and stop conditions
- Higheditorial warning
Turn off the breaker before cleaning the filter or grille. Mitsubishi Electric requires the supply to be disconnected before accessing terminals: do not open the indoor casing or the outdoor unit panels.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Mediumsource verified
Do not adjust the refrigerant charge or touch the service valves: the manual requires R410A-specific tools and refrigerant recovery, which only a certified technician can do.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Symptoms and causes
Probable causes · in order
- Clogged filterCommon
Mitsubishi Electric lists a clogged filter, which reduces airflow, as the first cause in both cooling and heating.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Air short cycling around an obstacleCommon
The manual cites short cycling of the air path (outlet air coming back in) and says to remove the obstacles causing it.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Operation outside the working rangePossible
Low load at low temperatures in cooling, or overload at high temperatures in heating, outside the unit's tolerance range.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Indoor fan or outdoor fan controlPossible
A defective indoor fan motor, a defective indoor controller board or a fault in the outdoor unit's fan control.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Refrigerant circuitPossible
Refrigerant overcharge, clogs in the circuit and, in heating, a defective bypass circuit in the outdoor unit.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Virtual technician
Does P6 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Mitsubishi Electric · 2016 · manual
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