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Mitsubishi Electric Air Conditioner U9 / UH Error Code
Power supply or current sensor problem. Here is what it means and how to clear it, easiest fix first.
The outdoor unit has detected a supply voltage outside its normal range, a fault in the signal it uses to time its power circuit, or a current sensor that isn't working.
Meanings can vary by outdoor unit series; check your manual.
How to fix Mitsubishi Electric U9 / UH
Check the breaker
Make sure the breaker for the outdoor unit is fully on. If it trips again when reset, leave it off.
Reset the power at the breaker
Switch off the breaker that feeds the air conditioner (some systems have separate breakers for the indoor and outdoor units, so switch off both). Wait about five minutes, switch the power back on and restart the unit to see if the code clears.
When to call a technician
If the code returns, have a technician or electrician check the supply and the outdoor electronics.
Parts that commonly cause U9 / UH
- power supply wiring
- current sensor
- outdoor control PCB
Order parts by your exact model number so they fit.
Other Mitsubishi Electric air conditioner codes
- Blinking OPERATION lightWall unit's indicator light is flashing
- P1Room air temperature sensor fault
- P2 / P9Indoor coil temperature sensor fault
- P4 / P5Drain sensor or drain pump problem
- PAShut down to prevent a water leak
- P6Freeze or overheat protection
- P8Pipe temperature error
- PbIndoor fan motor error
- FbIndoor control board error
- E0-E5Wall controller communication error
- E6 / E7 / E9Indoor and outdoor units aren't communicating
- U1 / UdHigh pressure or overheat protection
- U2Discharge temperature too high or low refrigerant
- U3 / U4Outdoor temperature sensor fault
- U6 / UP / UFCompressor overcurrent
- U8Outdoor fan stopped
- PLRefrigerant circuit abnormal
Frequently asked questions
What does U9 / UH mean on a Mitsubishi Electric air conditioner?
The outdoor unit has detected a supply voltage outside its normal range, a fault in the signal it uses to time its power circuit, or a current sensor that isn't working.
Can I fix Mitsubishi Electric U9 / UH myself?
Only the basic checks. You can safely try the steps above, but U9 / UH usually points to a part or fault that needs a technician.
What if U9 / UH keeps coming back?
A code that returns after a reset and the checks above usually means a part is wearing out. Note when U9 / UH appears (which cycle, how often) and have your model number ready; it helps a technician bring the right part on the first visit.
Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.