My Mitsubishi MSZ-FH09NA mini split head just started beeping. It beeps every 34 seconds whether on, off, or disconnected. This beep sounds slightly different than the on/off/function beep (quieter, a bit higher pitch, and possibly coming from a different internal location).

Other than the beep, the unit is apparently functioning. Fans, fins, cooling all working the same as before it started beeping.

I am not the original owner. I have lived in the house for ~ 2 years. I believe the system is > 5 years old. The system was recently serviced (several weeks ago) after a refrigerant leak caused by some contractors working on the exterior of the building. There are three heads in the home, and this is the only one beeping (for now).

I can't find anything about a beep in the manual. The fact that the beep continues when apparently disconnected makes me wonder if this is some sort of low battery signal (like a smoke detecter).

Help. Me. Make. It. Stop.

  • 1
    it wants something
    – Traveler
    Commented Jun 9, 2023 at 4:04
  • I think you are right about it being a low battery. The timing seems about right. The problem now becomes where it is coming from.
    – crip659
    Commented Jun 9, 2023 at 10:57
  • 2
    This person had "a low battery on an aftermarket drip pan water level sensor" reddit.com/r/hvacadvice/comments/ydjszk/… so it wouldn't be in the Mitsubishi unit's manual.
    – Ecnerwal
    Commented Jun 9, 2023 at 12:11
  • 1
    Silly question, but are you sure it's coming from the unit and not from somewhere else nearby (or from another part of your house and the beep is carrying from elsewhere)?
    – Milwrdfan
    Commented Jun 9, 2023 at 13:15
  • Apparently the unit beeps when you actuate the remote, so it could be the remote sending "Help, low battery" and the unit beeping in response. Commented Jun 9, 2023 at 19:16

1 Answer 1


Drain pan sensor, thanks @Ecnerwal: enter image description here

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