What it means
Used on indoor units with a drain pump and float switch, such as ceiling cassettes and some ducted units. Mitsubishi's SLZ-KF manual says that if the float switch is underwater for 1 minute 30 seconds with the drain pump running, the compressor and indoor fan are turned off, and it sets P5 if the float switch detects water again while the unit is held in that stopped state. With a wireless remote, the self-check reports it as 5 beeps and 5 flashes.
What to check, in order
- Switch the unit off
Turn it off at the controller and then at the breaker or isolator. Don't keep restarting it while the drain is backed up.
- Look for water
Check for drips or damp patches around the indoor unit and the ceiling. Mitsubishi's operating instructions say to stop using the unit and consult your dealer if water leaks from the indoor unit.
- Write down the code
Note the code and unit number for the engineer, as Mitsubishi's operation manual asks.
When to call an engineer
Call an air conditioning engineer (UK) or HVAC technician (US). They check whether the drain pump runs and water drains, and look for the causes Mitsubishi lists: a faulty or clogged drain pump, a blocked drain pipe, a stuck float switch or a faulty indoor control board.
A repair visit will usually check the drain pump, its filter and the route of the drain hose.
- Note the model and serial number. They're on a label on the side of the indoor unit, and on the outdoor unit.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the Mitsubishi P5 error code mean?
Water is not draining away from the indoor unit, so the float switch has stopped the unit to prevent an overflow. Used on indoor units with a drain pump and float switch, such as ceiling cassettes and some ducted units. Mitsubishi's SLZ-KF manual says that if the float switch is underwater for 1 minute 30 seconds with the drain pump running, the compressor and indoor fan are turned off, and it sets P5 if the float switch detects water again while the unit is held in that stopped state. With a wireless remote, the self-check reports it as 5 beeps and 5 flashes.
Can I fix Mitsubishi P5 myself?
Engineer only (engineer visit). Start with: switch the unit off; look for water; write down the code. Call an air conditioning engineer (UK) or HVAC technician (US). They check whether the drain pump runs and water drains, and look for the causes Mitsubishi lists: a faulty or clogged drain pump, a blocked drain pipe, a stuck float switch or a faulty indoor control board.
Is Mitsubishi P5 worth repairing?
Worth fixing. Mitsubishi's list points to a blocked drain, a failed drain pump or a stuck float switch. These are routine repairs, but get it done before water damages the ceiling.
Checked against
- Mitsubishi Electric SLZ-KF09/12/15/18NA1 ceiling cassette (M-series) Technical & Service Manual TCH118A (PDF)
- Mitsubishi Electric SLZ-M15-60FA ceiling cassette Technical & Service Manual OCH522 (PDF)
- Mitsubishi Electric SEZ-KD09/12/15/18NA(4) ducted (M-series) Technical & Service Manual HWE0802B (PDF)
- Mitsubishi Electric PCA-M35-140KA indoor unit Service Manual OCH659 (PDF)
- Mitsubishi Electric MSZ-GL06-15NA Operating Instructions (PDF)
- Mitsubishi Electric Air-Conditioners indoor unit Operation Manual BG79U581H01 (PLA, PKA, PCA, PSA, PEAD) (PDF)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.