What it means
Mitsubishi says P8 is not checked in Dry mode, and in cooling it takes at least 9 minutes to detect. In heating, it is flagged if the coil hasn't warmed up enough within 20 minutes of the compressor starting, so it takes at least 27 minutes to appear, and time spent defrosting isn't counted. With a wireless remote, the self-check reports it as 8 beeps and 8 flashes (SLZ-KF, SLZ-M and SEZ-KD manuals).
What to check, in order
- Write down the code
Note the code and unit number for the engineer, as Mitsubishi's operation manual asks.
- Switch off and on once
Turn the system off at the circuit breaker or isolator and back on, then run it normally. If P8 returns, leave it off and book a repair.
When to call an engineer
Call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi's list starts with too small a difference between the room and coil temperatures, caused by a shortage of refrigerant, a pipe sensor that has come off its holder or a refrigerant circuit fault. It also lists a faulty room or pipe sensor, an outdoor stop valve that is not fully open and, on systems with more than one indoor unit, crossed pipes or wiring.
A repair visit will usually check the refrigerant charge and the pipe joints for leaks, which needs a qualified refrigeration engineer.
- 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 P8 error code mean?
The indoor coil isn't getting cold enough in cooling, or warm enough in heating, compared with the room air, so the unit has stopped. A shortage of refrigerant is the first cause Mitsubishi lists. Mitsubishi says P8 is not checked in Dry mode, and in cooling it takes at least 9 minutes to detect. In heating, it is flagged if the coil hasn't warmed up enough within 20 minutes of the compressor starting, so it takes at least 27 minutes to appear, and time spent defrosting isn't counted. With a wireless remote, the self-check reports it as 8 beeps and 8 flashes (SLZ-KF, SLZ-M and SEZ-KD manuals).
Can I fix Mitsubishi P8 myself?
Engineer only (engineer visit). Start with: write down the code; switch off and on once. Call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi's list starts with too small a difference between the room and coil temperatures, caused by a shortage of refrigerant, a pipe sensor that has come off its holder or a refrigerant circuit fault. It also lists a faulty room or pipe sensor, an outdoor stop valve that is not fully open and, on systems with more than one indoor unit, crossed pipes or wiring.
Is Mitsubishi P8 worth repairing?
Get a quote first. Mitsubishi's first suspect is a shortage of refrigerant, which means finding and repairing a leak before recharging. Get a diagnosis and a quote first.
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)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.