Squeak Sound, HELP!!
 

I own a Jaguar XJ6 1995 and it always has a LOUD squeaky sound, Ive replaced both belts and the only time it stops squeaking is when I put on belt conditioner but then in around 10-15 mins it starts squeaking again LOUDY. Any Fixes?

check your crank damper for delamination; a/c idler pulley may be shot.

The whole A/C Compressor part is brand new, just replaced it

The compressor may be new but the idler pulley located between it and the crank pulley could still be at fault. I don't remember how many idler pulleys there are on a NA car, but probably at least 2.

It's your harmonic balancer more than likely. Make a mark across the pulley with chalk, start the car with all body parts clear of the engine. Shut the car off and check the line . If it's no longer connected as you made it the balancer needs to be rebuilt.