I'm trouble shooting my horn on my 85. I have replaced the buton on the steering wheel and it is working but I do not get 12v at the horns. I purchased the 30v relay as the next step but I can not find it on the car. Where is it located??? Also am I supposed to get 12v at the horn button? I only get .3v (I'm thinking this is the low voltage side of the relay)
I have Chiltons and Hayes manuals but they do not show locations of many electrical componets, is there a better manual out there?

The relay is located behind the center information display above the radio.

The GM manuals are the best. Check ebay.

My horn is fixed, turned out to be a bad relay, bad 10v fuse, bad button on the wheel and finally one of the horn units itself. phew... Locating the relay and fuse was the hard part, overall a good learning experence.