Loud Screeching sound

[Noquacks]

People,

1987 Sunbird, when I switch on the ac button to activate compressor there is immediately a loud screeching sound from the comp area. It stops after about 7-8 seconds. Vents put out ice cold ac. Then, every about 5 minutes the sound comes back, then again, goes away. Could it be the loose ac belt needing tightening? Maybe low on compressor oil?

Thanks, people.

[Cusser]

Could it be the loose ac belt needing tightening?

That should be easy enough to check.

I might pull the belt, and check any tensioners and AC clutch pulley bearings for drag or noise. And maybe install a brand new belt.

[Noquacks]

Could it be the loose ac belt needing tightening?

That should be easy enough to check.

I might pull the belt, and check any tensioners and AC clutch pulley bearings for drag or noise. And maybe install a brand new belt.

Thanks, Cusser. Good tips. Will try those checks this weekend!

[Noquacks]

I tightened the belt a bit, actually, to the max setting, which I thought was not a good situation for a belt to tight on the max slider notch. Started the car, and the squeal almost disappeared. But i watched the belt as it turned with ac on, and the upper edge of it was wobbling a distance of say, 1/2" up/down. is that normal? It would indicate the belt could be stretched, right? Especially even with it being tightened to the max arc setting.

[JohnHere]

1987 Sunbird, when I switch on the ac button to activate compressor there is immediately a loud screeching sound from the comp area. It stops after about 7-8 seconds. Vents put out ice cold ac. Then, every about 5 minutes the sound comes back, then again, goes away. Could it be the loose ac belt needing tightening? Maybe low on compressor oil?

Your car is well within the R-12 era. As far as you know, has the system been converted to R-134a, or is it still R-12? The reason I ask is because the conversion, if completed, might not have been done correctly, causing problems now with the compressor.

[Noquacks]

It has been on R134a for 20 years. That is not the problem. But good point!

[JohnHere]

It has been on R134a for 20 years. That is not the problem. But good point!

I don't know your car's service history (not much, anyway). But if the compressor is the original since the system's conversion to R-134a, and even before that (it could be a GM R4, which isn't known to be the greatest compressor in the world), it might be starting to disintegrate internally and seize-up at times, causing the occasional belt squeal.

One way to find out is to recover the refrigerant and pull-out the orifice tube (OT). If the OT is full of black gunk and "glitter," then you'll know for sure that the compressor is on its way out.