- HVAC
- Air conditioner
PA
Mitsubishi Electric PA on an air conditioner: water leak stop
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
High
Quick answer
On Mitsubishi Electric PKA wall units, PA is a forced compressor stop because the unit thinks condensate water is not draining. Look for dripping water: if it drips, turn off the power and call a technician; if not, do a single reset.
Safety first
Stop and check this first
- Water and electricity do not mix: if the unit drips onto sockets, extension leads or appliances, switch off the breaker before drying and keep it off until a technician has inspected it.
- Mitsubishi Electric requires every supply circuit to be disconnected before terminals are accessed; the pump, float switch and board sit inside the casing, which you should not open.
Safe checks you can perform
- Confirm PA on the remote
- Look for water before any reset
- Air filter with the power isolated
- Drain pump and float switch test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Drain test from the service menu
- Do not attempt this professional task: Float switch measurement
- Do not attempt this professional task: Thermistor and multi-unit installation 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.
Drain test from the service menu
What they doThe technician uses the remote's drain pump test run and checks that water actually leaves through the hose.
They must show youwater flowing out of the drain during the pump test.
In writingcode PA, the drain test result and what was cleaned or replaced.
Float switch measurement
What they doThey measure the float switch resistance, inspect its connector and check that the lead does not carry water down to the sensor.
They must show youthe measured float switch resistance and how its lead is routed.
In writingthe float switch reading, connector condition and the reason for any replacement.
Thermistor and multi-unit installation check
What they doThey compare the room and liquid pipe temperatures shown by the controls with reality and, with several indoor units, inspect the piping and connecting wires.
They must show youthe temperatures read on the remote and on the outdoor board against the real ones.
In writingreadings taken, connections inspected, final diagnosis and date.
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 PA on the remote
- Who:
- you.
- How:
- on the wired remote, open the main menu with MENU and go to Error information, which shows the check code and refrigerant address. With the wireless remote, press CHECK twice, pick the address with TEMP and press HOUR aimed at the receiver: PA appears as 5 blinks and beeps.
- Result that matters:
- knowing the stop is caused by PA and not by another drain warning.
- If the wired remote shows PA:
- carry on with this page.
- If you only have the wireless remote and count 5 blinks:
- PA and P5 (drain pump error) share that pattern, so pass it on to the technician exactly as seen.
- Evidence to keep:
- a photo of the remote display or a video of the blinking lamp, with date and time.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Look for water before any reset
- Who:
- you, opening nothing.
- How:
- check the indoor unit, the wall and the floor below it: drops on the casing, damp patches or pooled water. If there is water near the unit or near sockets, switch off the unit's breaker before drying anything.
- Result that matters:
- deciding whether it is safe to restore power once.
- If it drips or the wall is damp:
- keep the power off, protect the floor and call the technician; do not reset it.
- If everything is dry:
- do one reset from the breaker, because the manual says PA is only cleared by resetting the main power.
- Evidence to keep:
- photos of the area under the unit and a note of whether water was present.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Air filter with the power isolated
- Who:
- you, with the unit isolated.
- How:
- with the breaker off, open the indoor unit's front grille as your unit's operation manual explains, take out the filter and see whether dust is blocking it. Clean it as that manual says, let it dry and refit it before switching the power back on.
- Result that matters:
- ruling out a clogged filter, which the manual links to sloshing water wetting the float switch.
- If the filter was heavily clogged:
- after cleaning it, watch whether PA returns over the next days.
- If the filter was clean:
- the cause is in the drain or the float switch, which the technician checks.
- Evidence to keep:
- a photo of the filter before and after cleaning, and the date.
Only with the power isolated, touching nothing behind the grille except the filter.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Drain pump and float switch test
- Who:
- an HVAC technician.
- How:
- runs the drain pump test from the remote's service menu, confirms water leaves through the drain, measures the float switch resistance, inspects its connector and how its lead is routed.
- Result that matters:
- whether the fault is a blockage, the pump, the float switch or condensation on it.
- If no water comes out or the pump does not respond:
- the drain is cleared or the pump replaced.
- If draining works:
- the thermistor readings are checked and, on multi systems, the piping and wiring between units.
- Evidence to keep:
- the drain test result, the measured float switch resistance and the connector condition.
Work inside the indoor unit with water close to the board: technician only, with the power isolated for measurements.
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 PA
- Mitsubishi PA
- Mr. Slim PA
- PKA PA
What it means
Service manual OCH639 for the PKA-A24/30/36KA7 indoor units defines PA as a forced compressor stop due to a water leakage abnormality: the drain float switch senses water for more than 15 minutes while a temperature condition between intake air and the liquid pipe adds up to 30 minutes. Once detected, the abnormality is not released until the main power is reset. On other models the code may mean something else. Seeing PA on the display is not enough to call any part faulty.
Warnings and stop conditions
- Higheditorial warning
Water and electricity do not mix: if the unit drips onto sockets, extension leads or appliances, switch off the breaker before drying and keep it off until a technician has inspected it.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Mediumeditorial warning
Mitsubishi Electric requires every supply circuit to be disconnected before terminals are accessed; the pump, float switch and board sit inside the casing, which you should not open.
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
- Drain pump or drain pipe blockedCommon
Mitsubishi Electric lists drain pump trouble first, then defective draining caused by a clogged drain pump or drain pipe.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Float switch open or badly connectedPossible
An open circuit in the float switch or poor contact at its connector, which the technician checks by measuring the float switch resistance.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Condensation on the float switchPossible
Water running down the float switch lead, or water sloshing in the pan because the filter is clogged, as the service manual itself describes.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Twin, triple or quadruple installationLess common
In systems with several indoor units, a piping connection that differs from the plan or crossed wiring between units also appears as a cause.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Wrong thermistor readingsPossible
Faulty detection by the room temperature thermistor or the liquid pipe thermistor can distort the temperature condition the detection relies on.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Virtual technician
Does PA 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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