Awful screech/squeal when a/c or defrost on

[Yorb]

Hi guys, I have an S13 hatch that makes the loudest, most awful screeching noise when the A/C is on OR one of the window defrost/defog buttons is on. Doesn't matter what the fan is set on, 1, 2, 3, or 4.

I think this is the auxiliary fan, or a/c fan, or whatever it's called -- the one between the engine fan and the radiator, because it doesn't turn until I have the cabin fan on and push one of those 3 buttons (A/C or the 2 far right window vent buttons). Then it turns but I can't stand the noise long enough to figure out where it's coming from.

Searching turns up either a fan motor or fan clutch causing a belt to slip, but I don't have the problem everyone else does where it makes noise above 3000 rpm. ONLY when that aux fan comes on.

What do I replace?

Thank you!

[Razi]

I'd take a peak inside the engine bay with a flashlight and check where the squeal is coming from.
Could be a worn belt.

[Cone Killer]

Yup sounds like a loose belt is squealing when the compressor clutch engages. Which is does when the AC or Defrost is turned on.