Expert: Rob Painter - 11/2/2011

Question
Horn doesn't work.  Relays under glove box, and under hood (is there one under hood for horn and if so, which one?) as well as fuses under steering column (medium size), under glove box (micro size), and large one under hood in engine compartment all seem to check out. Horn button on steering wheel seems to be working, but none of the 4 horns work. When I use a jumper (under glove box horn relay) to cross the two terminals (relay out) that should make the horn work, I only get a slight voltage drain (no blown fuses) but still no horn.  Any troubleshooting procedures?  It seems odd that I cannot even get the horns to blow by jumping the relay under the glove box.  There seems to be little or no information on the NET concerning a 1991 Deville issue like this.

Answer
Hello,

The horn circuit on this car is rather simple. You did not say if you had someone pushing the horn pad to see if you were getting voltage to the horns themselves.
You have an old car here. All 4 horns could be junk, although unlikely with the minimum voltage coming from the relay.

Then there is the turn signal switch inside the steering column that needs to be checked. You could have a bad ground in the column at the cancel cam. The TS has a horn button on it that contacts the cancel cam .

You have the horn pad (air bag). Under that is the wires that hook into the horn button of the cancel cam. You press down on the button and turn counter clockwise. The wire comes out. A puller is needed for the steering wheel. Don't use a hammer!The clock spring snap ring is removed. The clock spring is removed. A puller is required to pull the lock plate is removed with a puller. The cancel cam is removed. Then you will see the horn button sticking out of TS. Take a screwdriver and ground the button to the shaft. If not working and horns are good you need ts.

If it does work, then there is an issue with the cam, or horn pad.

You are not alone in not thinking about the t.s., but sometimes trying to fix the simplest things, it can turn into a nightmare leaving one scratching their head. Especially on an older car. I would highly recommend if you are keeping the car that you attempt to get a factory service manual for the car. You should be able to find one on Ebay. Don't screw around with general manuals like Haynes, Chilton etc.
You will find the factory service manual the best investment you have made for the vehicle. Here you get diagnostic flow charts, schematics and everything else you need.
Thank you so much for the great rating!

Rob

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