What causes Mitsubishi Mini Split P5?

The drain pump isn't working, so condensate builds up in the drain pan until the float switch lifts. A clogged drain pump, from slime or debris in the pan or pump inlet. A clogged or poorly sloped drain pipe, so the pump runs but the water can't leave. A stuck float switch. Mitsubishi notes that a catch or slime on the moving part can make the switch read underwater even when it isn't. A failed float switch that reads closed (underwater) even with the float down. A defective indoor controller board, which Mitsubishi lists last, after the pump, drain and float switch check out.

How do I fix Mitsubishi Mini Split P5?

Write down the exact code and how the remote showed it. P5 is a drain problem, while P4 is the float switch connector and PA is a forced stop for a water leak, and a technician will want to know which one you saw. Switch the system off at the breaker before looking at anything. Mitsubishi's manuals say to turn the power off and on again after the checks, and on City Multi systems the forced stop can't be cleared from the remote, only by a power reset. Check the drain line where it exits the building or empties into a drain. If it is dry while the system has been cooling, or water is backing up, the line or pump is the likely problem. Clean the indoor unit's air filters. Mitsubishi's City Multi chart includes checking for a clogged filter in its 2502 checklist. If you can safely reach the outside end of the drain line, clear any visible blockage there. Don't remove the cassette panel or drain pan yourself unless your owner's manual covers it. Watch for water dripping from the ceiling around the unit. If it is leaking, leave the system off and put a towel or bucket under it until it is serviced. Restore power and run cooling. If P5 comes back, the pump, float switch or board needs a technician.

When should I call a pro for Mitsubishi Mini Split P5?

P5 returns after a power reset. A technician checks whether the drain pump actually runs and moves water, which is Mitsubishi's first check. The pump runs but water doesn't drain. The drain pump inlet and the drain piping need to be cleared, and the pipe slope checked. The drain works but P5 keeps coming back. The technician unplugs float switch connector CN4F and checks it reads closed with the float up and open with the float down, and replaces the float switch if it reads closed with the float down. The pump, drain and float switch all check out. Mitsubishi's remedy is to replace the indoor controller board if the error comes back with the float switch connector correctly reading open. There is water damage to the ceiling, or the system is new or under warranty. Contact the installing contractor or a Mitsubishi Electric Diamond Contractor.

Code: P5🔧 Mitsubishi Mini Split

Mitsubishi Mini Split Error Code P5: Drain Pump Error, Drain Overflow Protection (Meaning, Causes, Fixes)

Q: What does Mitsubishi Mini Split P5 mean?

P5 on a Mitsubishi Electric indoor unit with a built-in drain pump (such as a ceiling cassette) means drain overflow protection has tripped. The drain float switch stayed underwater while the drain pump was running, so the unit shut off the compressor and indoor fan to keep condensate from overflowing. Mitsubishi's service manual points to a failed or clogged drain pump, a clogged drain pipe, a stuck or faulty float switch, or, last, the indoor control board. On City Multi systems the same fault shows as code 2502. Mitsubishi Electric's PLA-A BA4 ceiling cassette service manual (OCH482) lists P5 as "Drain pump error" in its check code table and describes it as drain overflow protection operation. If the drain float switch is detected underwater for 1 minute 30 seconds continuously with the drain pump on, the unit treats it as a suspended abnormality and turns off the compressor and indoor fan. If the same condition is detected again during that suspended state, the drain pump is judged abnormal and P5 is shown. On the wireless remote's self-check, P5 is reported as 5 blinks or beeps (the same count as PA). Mitsubishi's City Multi error code chart lists four-digit code 2502 as "Drain overflow protection (P5)", and the City Multi service handbook calls 2502 a drain pump fault, detected when the float switch has stayed on for 3 minutes after the sensor tip was first found underwater. Neighboring codes: P4 (5701) means the float switch connector is open, and PA (2500) is a forced compressor stop due to a water leakage abnormality.

Reviewed 2026-10-24 · Based on 3 manufacturer & service sources

What the code means

Mitsubishi Electric's PLA-A BA4 ceiling cassette service manual (OCH482) lists P5 as "Drain pump error" in its check code table and describes it as drain overflow protection operation. If the drain float switch is detected underwater for 1 minute 30 seconds continuously with the drain pump on, the unit treats it as a suspended abnormality and turns off the compressor and indoor fan. If the same condition is detected again during that suspended state, the drain pump is judged abnormal and P5 is shown. On the wireless remote's self-check, P5 is reported as 5 blinks or beeps (the same count as PA). Mitsubishi's City Multi error code chart lists four-digit code 2502 as "Drain overflow protection (P5)", and the City Multi service handbook calls 2502 a drain pump fault, detected when the float switch has stayed on for 3 minutes after the sensor tip was first found underwater. Neighboring codes: P4 (5701) means the float switch connector is open, and PA (2500) is a forced compressor stop due to a water leakage abnormality.

Likely causes

The drain pump isn't working, so condensate builds up in the drain pan until the float switch lifts.
A clogged drain pump, from slime or debris in the pan or pump inlet.
A clogged or poorly sloped drain pipe, so the pump runs but the water can't leave.
A stuck float switch. Mitsubishi notes that a catch or slime on the moving part can make the switch read underwater even when it isn't.
A failed float switch that reads closed (underwater) even with the float down.
A defective indoor controller board, which Mitsubishi lists last, after the pump, drain and float switch check out.

Safe DIY checks

⚠ Before you start

Turn off the breaker (or breakers) for the indoor and outdoor units before any inspection. Ceiling cassettes are overhead and wired to line voltage, and water near electrical parts is a shock risk, so leave panel removal, the drain pump, the float switch and the control board to a licensed HVAC technician. Never jumper or bypass the float switch; it is what keeps condensate from overflowing into your ceiling.

Write down the exact code and how the remote showed it. P5 is a drain problem, while P4 is the float switch connector and PA is a forced stop for a water leak, and a technician will want to know which one you saw.
Switch the system off at the breaker before looking at anything. Mitsubishi's manuals say to turn the power off and on again after the checks, and on City Multi systems the forced stop can't be cleared from the remote, only by a power reset.
Check the drain line where it exits the building or empties into a drain. If it is dry while the system has been cooling, or water is backing up, the line or pump is the likely problem.
Clean the indoor unit's air filters. Mitsubishi's City Multi chart includes checking for a clogged filter in its 2502 checklist.
If you can safely reach the outside end of the drain line, clear any visible blockage there. Don't remove the cassette panel or drain pan yourself unless your owner's manual covers it.
Watch for water dripping from the ceiling around the unit. If it is leaking, leave the system off and put a towel or bucket under it until it is serviced.
Restore power and run cooling. If P5 comes back, the pump, float switch or board needs a technician.

🛠 When to call a pro

P5 returns after a power reset. A technician checks whether the drain pump actually runs and moves water, which is Mitsubishi's first check.
The pump runs but water doesn't drain. The drain pump inlet and the drain piping need to be cleared, and the pipe slope checked.
The drain works but P5 keeps coming back. The technician unplugs float switch connector CN4F and checks it reads closed with the float up and open with the float down, and replaces the float switch if it reads closed with the float down.
The pump, drain and float switch all check out. Mitsubishi's remedy is to replace the indoor controller board if the error comes back with the float switch connector correctly reading open.
There is water damage to the ceiling, or the system is new or under warranty. Contact the installing contractor or a Mitsubishi Electric Diamond Contractor.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Condensate drain pump

A failed or clogged drain pump is Mitsubishi's first listed cause for P5; match the exact indoor model number before ordering.

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⚙

Drain float switch

Replace if it reads closed (underwater) with the float down, per Mitsubishi's check.

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⚙

Wet/dry vacuum

Handy for clearing a clogged condensate line from the outside end.

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Sources

Last reviewed 2026-10-24. Always confirm against the manual for your exact model number.

Mitsubishi Mini Split Error Code P5: Drain Pump Error, Drain Overflow Protection (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

Condensate drain pump

Drain float switch

Wet/dry vacuum

Related codes

Sources