Strange squealing noise
 

When I hit 70 mph I get a squealing noise kinda like a bearing going out. If I turn my ac off it will stop but comes back even with the ac off. It comes and goes. I'm thinking ac compressor. Any ideas anyone?

does it come back on in the defrost mode?

Don't know. I haven't tried that yet but it feels like it pulls the motor down when it does it

Check the idler; I've heard of them causing problems like the "unknown squeal" that you can't find.

Have you figured out what is causeing this problem yet? we have 2 trucks that do the exact same thing and have had them in the shop several times and its still doing it

Pull the serpentine belt off and check idler pulley, fan support pulley, and tensioner pulley. Those are the normal problem children.

The AC pump, PS pump, and water pump could also be a problem so make sure they are quiet. Belt could just be bad also, don't forget it.

No I haven't. I've had people tell me it could be the idler, belt tensioner, water pump or ac compressor. But I think I'm gonna replace the tensioner first and go from there. It's the least expensive to start out with