Quick answer: The Mitsubishi P5 error code on a ducted aircon (Mitsubishi Electric Mr Slim PEAD) is a drain pump error. The float switch in the drain pan keeps detecting water while the pump runs, so the unit stops. Mitsubishi lists a clogged drain pump or pipe, a faulty pump or float switch, or the control board. Switch it off and call a technician.
Written by Ofek Shamir, owner of The Guys Group · Updated 29 September 2026 · Sources: Mitsubishi Electric manuals, linked below.
What does P5 mean on my Mitsubishi aircon?
P5 on a Mitsubishi Electric ducted unit is “Drain overflow protection operation”, shown on the wired controller as a drain pump error. When the float switch in the drain pan stays under water for 1 minute 30 seconds with the drain pump running, the unit turns off its compressor and indoor fan. If that happens again, it logs P5.
Mitsubishi Electric’s service manual for PEAD-M ducted units lists four causes:
- “Malfunction of drain pump”
- “Defective drain”, listed as “Clogged drain pump” and “Clogged drain pipe”
- “Defective drain float switch”, where the float catches or sticks and reads as under water
- “Defective indoor-controller board”
Mitsubishi’s checks are technician work: test the drain pump, the drain function and the float switch, and only then turn the power off and on again.
What does P6 mean on my Mitsubishi aircon?
P6 on a Mitsubishi Electric ducted unit means “Freezing/overheating protection is working”: the indoor coil got too cold in cooling mode or too hot in heating mode. For both modes, the first cause in Mitsubishi’s service manual is “Clogged filter (reduced airflow)”, and the first check it gives is “Check clogging of the filter.”
In cooling, the unit pauses for six minutes if the coil stays below −15°C for three minutes after the compressor starts. In heating, it pauses if the coil goes above 70°C. If the same thing happens again shortly after the pause, it shows P6.
A clogged filter is only one cause. Others include a “Short cycle of air path”, a defective indoor fan motor or controller board, “Defective outdoor fan control”, “Overcharge of refrigerant” and a “Defective refrigerant circuit (clogs)”. If P6 returns once the filter is clean, a technician needs to find the cause.
What does PA mean on my Mitsubishi aircon?
PA on a Mitsubishi Electric ducted unit means “Water leakage”, and it is also listed under the four-digit code 2500. The unit raises it outside cooling and dry modes when the drain float switch has been sitting in water for 15 minutes or more and the coil pipe has been reading more than 10°C colder than the incoming air for 30 minutes.
Mitsubishi lists six possible causes:
- “Mis-piping of extension pipes” (multi-unit systems)
- “Mis-wiring of indoor/outdoor unit connecting wire” (multi-unit systems)
- a detection failure of the inlet or pipe thermistor
- “Drain pump failure”
- “Drainage failure”, listed as a clogged drain pump and a clogged drain pipe
- “Drain float switch failure”
The manual also says: “When this error is detected, the error will not be reset until the main power is reset.” With six possible causes, PA needs a technician to diagnose.
Where do I see the Mitsubishi error code, and why is the light flashing?
On a Mitsubishi Electric ducted unit with a wired controller, the error code appears on the controller screen. Mitsubishi’s Australian manual says the green ON/OFF lamp “blinks while the remote controller is starting up or when there is an error”. With a wireless remote, the operation lamp next to the receiver on the indoor unit flashes instead.
On the PAR-41MAA wired controller, the error screen shows the “Error code, error unit, refrigerant address, unit model name, date and time on which an error occurred, and serial number” (model and serial only if registered). For a flashing lamp, the Australian manual says “the unit needs to be inspected. Consult your dealer for service.”
Mitsubishi’s service manual matches flash counts to codes. Five flashes is P5 and six is P6, but only for errors detected by the indoor unit. Faults detected by the outdoor unit use their own list with the same flash counts, so a flash count alone does not confirm the code.
What do the other Mitsubishi error codes mean?
These are the indoor-unit codes in Mitsubishi Electric’s service manual for PEAD-M ducted units, with the matching flash count. Codes can mean different things on other model families and on the outdoor unit, so use this table to brief your technician, not to diagnose.
| Wired code | Lamp flashes* | Mitsubishi’s meaning | Can I do anything? |
|---|---|---|---|
| P1 | 1 | Intake sensor error | No. Call a technician. |
| P2, P9 | 2 | Pipe sensor error (the liquid pipe, or the coil pipe where the refrigerant is part liquid, part gas) | No. Call a technician. |
| E6, E7 | 3 | Indoor/outdoor unit communication error | No. Call a technician. |
| P4 | 4 | Drain sensor error (contact failure of the drain float switch connector) | No. Call a technician. |
| P5 | 5 | Drain pump error (drain overflow protection) | No. Call a technician. |
| P6 | 6 | Freezing/overheating safeguard operation | Check the return air filter (power off). If it returns, call a technician. |
| EE | 7 | Communication error between indoor and outdoor units | No. Call a technician. |
| P8 | 8 | Pipe temperature error | No. Call a technician. |
| E4 | 9 | Remote controller signal receiving error | No. Call a technician. |
| Fb | 12 | Indoor unit control system error (memory error, etc.) | No. Call a technician. |
| PL | 14 | Refrigerant circuit abnormal | No. Call a technician. |
| PA | Not in the flash table | Water leakage (2500) | No. Call a technician. Needs a main power reset to clear. |
* Flash counts apply only to errors detected by the indoor unit.
For P8, Mitsubishi’s listed causes start with “Shortage of refrigerant”; for E6, they include faults in the indoor/outdoor connecting wire. Other brands use different codes. See Daikin A3 and A5 error codes, LG CH04 and CH61 error codes, or our guide to ducted air conditioner error codes across brands.
Can I reset a Mitsubishi error code myself?
Mitsubishi Electric’s first instruction is not to: when an error code appears, the Australian manual says “Do not attempt to repair this equipment by yourself. Turn off the power switch immediately and consult your dealer.” Some wired controllers do have an error reset, but it does not fix whatever caused the code.
The PAR-41MAA instruction book first says “Check the error status, stop the operation, and consult your dealer.” It then says “Press the F4 button or the ON/OFF button to reset the error that is occurring”, confirming with “OK”. Mitsubishi’s service manual has technicians reset the code logs “after finishing service”. PA only clears with a main power reset. Other controllers differ, so check your instruction book.
With P5 or PA, the float switch has already found water, so don’t use the reset to keep the unit running. If the code comes back, leave it off and call a technician.
Is it safe to keep running my Mitsubishi aircon with P5 or PA showing?
No. Mitsubishi Electric’s instruction for an error code on these units is to “Turn off the power switch immediately and consult your dealer”. With P5 or PA, the unit’s own float switch has already detected water standing in the drain pan. Mitsubishi describes an error code as the protection devices having “operated to protect the air conditioner”.
What can I safely check myself?
The only owner check Mitsubishi Electric gives for these units is the air filter. Its Australian manual says to “Clean the filter. (Airflow is reduced when the filter is dirty or clogged.)” It also says: “Before you start cleaning, stop operation and turn OFF the power supply.” Leave the drain pan, drain pump, float switch and wiring to a technician.
Mitsubishi’s steps: “Clean the filters using a vacuum cleaner”, or wash very dirty ones in lukewarm water (not above 50°C) and dry them fully out of direct sun. Don’t wait for a reminder: the Australian installation manual lists “No filter sign indicator” as an installer setting. Mitsubishi Electric Australia also notes that “Some air conditioners, such as ducted, cassette bulkhead systems and outdoor units, may require professional cleaning methods.”
I have a Mitsubishi wall split, not ducted. Do these codes apply?
Probably not in the same way. Mitsubishi Electric’s Malaysian troubleshooting page explains how to show a two-digit code by holding the CHECK button on the handheld remote. The codes it lists do not include P5, P6 or PA, and its advice for any code is to “Stop using the air conditioner, turn off the breaker, and contact your dealer.” Australian models can differ, so check your own manual.
What should I tell the technician?
Give the technician the code and the model name. Mitsubishi Electric’s Australian manual says to “provide the dealer with the model name and information that appeared in the remote controller display”. A photo of the error screen does this, and also shows the error unit and, if registered, the serial number. Note whether the unit was cooling or heating.
Who do I call: a technician or a cleaner?
Codes like P5, PA or P8 need a qualified air conditioning technician. If your filter reminder is on, the return air filter is caked with dust or the system just hasn’t been cleaned in a while, The AC Cleaning Guys can help. Our ducted system clean is $349 + GST and includes a new filter, cleaning of the aluminium duct foils from the filter through to the return duct, a professional sanitise, and an airflow check and test run, with no mess left behind. If you prefer to keep your current filter, our Deep Scrub & Sanitise option is $229 + GST: the duct foils deep-scrubbed through to the return duct, a professional sanitise, and an airflow check and test run. See our ducted aircon cleaning service or call 1300 380 090.
The AC Cleaning Guys is an independent cleaning company, not affiliated with or authorised by Mitsubishi Electric.
Sources
- PEAD-M ducted service manual (HWE16130), Mitsubishi Electric: code list p.35, P4 and P5 p.37, P6 and P8 p.38, E6 and PA p.40
- PEAD-M ducted operation manual, Mitsubishi Electric Australia: lamps pp.3 and 5, filter cleaning p.9, troubleshooting pp.10–11
- PEAD-M ducted installation manual, Mitsubishi Electric Australia: filter sign setting
- PAR-41MAA controller instruction book, Mitsubishi Electric: error information pp.75–77
- How to clean your air conditioner filter, Mitsubishi Electric Australia
- Troubleshoot air conditioners, Mitsubishi Electric Malaysia
