When I finally found out my power antenna relay was the cause of my antenna problems I searched and couldn't find the part# for it on the board so here they are if it helps anyone in the future:

GM Part# (from my 1986 Camaro) - 10028531

Cross references with these other manufacturers:

Airtex/Wells: 1R1459
Standard Motor Products: RY603
BWD Automotive: R3124
Autozone: 20118 (Alternate# 41-5603)

Also, the bracket with the relay on it behind the dash is held in with two 7mm bolts. A bit of a pita to remove but a 1/4" ratchet with a universal gets it done quick enough.

how much does it cost?

Autozone's price was $23.89 out the door. Price varied slightly on eBay but about the same.

What kind of problems were you having with your power antenna?

The reason I ask is because I have an aftermarket head unit in my IROC and when I try to use the tuner to get radio I can't even get one station, and when I do it is barely audible!

My antenna going up and down was working intermittently until it just stopped. I have an aftermarket radio also and I can tell you 100% the relay is not your problem.

It sounds like you have a connection issue someplace. The cable that provides the signal from the antenna itself to the radio is a thick black cable which connects directly behind the radio and runs to the antenna mast housing where it is held on with two screws. You will get signal with it connected regardless if the power parts of the antenna are disconnected as long as the mast is up.

First I'd pull the radio and see if the antenna cable has pulled out the back of the unit. This would be my first guess. Possibly it wasn't put all the way in when the radio was installed or fit too loosely and fell out. If that's the case slightly bend up the two side tab things on the connector to make it fit a little tighter and plug it back in (it will make sense when you're looking at the plug)

If that checks out I'd pull the front passenger wheel, remove the wheel well trim and look inside at the antenna and make sure the antenna is attached to the mast (which it should be unless someone was in there messing with it)

Last I'd trace the cable from the radio to the antenna to see if it has been broken somehow (that would be odd but people do crazy things so you never know)