[raymo]

Anyone here with extensive knowledge of reverse cycle a/c units?
My Fujitsu 7kw unit most of the time makes a sort of low whistling noise
which is cyclic, whistles for about 2 secs, becomes much lower volume for about 2secs, and then returns to its original volume; repeats this
ad infinitum. It is not loud; just audible enough to drive me insane.
As far as I know there are no oscillating parts in an a/c, [ the vane swing feature is disabled] ,and altering the fan speed doesn't affect the noise.
All suggestions or comments welcome.
raymo