MSZ-GA50VA Turning Itself On

[wavering]

I have two Misubishi MSZ-GA50VA units on my wall put there by the developers when the place was built a couple of years back so all virtually new kit.

I turned them on for the first time yesterday (I bought this place in April 2009). They both work and I have downloaded an operating manual so both remote controls are now set on manual control. Despite this, the one on the right switches itself on every few hours for no apparrent reason. When this happens the remote control appears to be switched off (ie the display is not "on")

Both remotes are infra red so it is not people next door turning their units on.

Any ideas? I can turn it off totally via the breakers but this is a bit crummy. Neither unit has turned itself on before - just after I started using it yesterday ...
.

[sinewave]

I've had this on another manufactures kit.

It was a faulty IR sensor on a small pcb board which was effected by strong sunlight and switched the unit on in the afternoons.