Idler pulley went out...Part #?

The idler on my xj squeals really bad when the a/c is turned on. It doesn't make any noise without the air on, but it's winter and i need to fix this thing.

I just called all the parts places and they have a few different idler's available, so I'm not sure which one i need. Its the one right next to the a/c compressor. Does anyone know a part number for that or what I should tell the parts store to get the right one?

Just sounds wierd that it is only noisy with the air on??????? Could it be the belt tension or the compressor? These are very sensitive to low belt tension.

Check the belt tension first. if it continues it could either be the ilder pulley cheap and (easy to replace) or the harmonic balancer.

I've checked the belt tension and it's fine.

I just replaced mine because it was only making noise when it was cold. But I didn't have any issues at the parts store. I just went in and asked for the one up top and they gave it to me.

First take the belt off and spin each pulley by hand. You should be able to tell if one of them is bad.

When I did this, I found that my idler pulley was very obviously shot. The parts store had two different ones. One was a smooth pulley and the other was a serpentine-grooved pulley.

Just take the old one off and take it to the store with you.