Horn don't work, where should I start

[KenD]

My horns gave out. First it was the one behind the battery and then the one by my passenger side fog light gave out. I went to the junker and pulled both horns out of an older Pontiac Grand Prix and went to replace them. No joy. I don't know what the chances of both replacement horns are being bad, but it would be minimal I would think.

Where else should I look?

Ken

[The Fred]

Fuses? Did you check the fuses?

Jumper a wire to the horns and see if they will work.. watch your ears.

Nice avatar there nothing like jumping breasts for scenery

[KenD]

I know that there is one 30amp under the hood for the horns, power seats etc, but everything that is supposed to be connected to that fuse works except the horn.

Not quite sure where to start to jump the horn. Could you elaborate?

[JimD]

Find the horn relay and temporarily replace it with a known good relay as a test.

[KenD]

okay, uh, any idea on where the relay may be located JimD? Under the hood or in the car itself.

[JimD]

Beats me. But I would expect it to be under the hood.

Someone with your year/model Service Manual might help you.

[KenD]

found it and swapped it with my fuel pump relay and still no go. It was working about 2 months ago, well one of them was and now nothing. I would hate to bring it to the dealership for something electrical. I might as well just remortgage the house now. lol

[stefank]

Ken,

did you check the horns themselves by applying ground and power to the connectors at the horn? As Fred said, they can be loud, so be careful.

Stefan

[KenD]

How would I do this Stefan? What power source would I have to use?

[stefank]

Ken,

I usually have an old battery around so I just connect pos and neg to the battery poles and jumper these leads to the horn.

If the horn has two prongs in the connector, connect one to the positive and one to the negative side of the battery.

You should use an inline fuse in the positive wire to be on the safe side. If the horn is mounted to the car's body, you should check if one of the prongs is directly connected to ground. Do not connect this contact with the positive side, especially if you use the car's own battery!!

If the horn has only one prong, connect this to the positive and the mounting bracket to the negative side of the battery.

Have to go to bed now, it's 2:00 am here, otherwise I'll fall asleep on my desk...

Stefan

[KenD]

thank you stefan, i will use my boat battery. Yes, they are the two prong connectors

Ken

[The Fred]

The horns are alot louder than you think.. be careful of your ears.

Wear hearing protection or wire the horns and go over to the battery and connect it there so you aint right by the horns.

[Cadillac Jim]

The 1997 shop manual, which has electrical diagrams for E/K and DeVille, has two circuit diagrams for horns. The difference is that one has two horns and the other has four. This should be accurate for your 1994 STS.

The two-horn diagram has horns with "A" note and "F" note. You must get replacement horns with the same pitch or it will sound like a Fiat or whatever.

The four-horn diagram, apparently for Deville or commercial chassis, has "A", "C", "D", and "F" notes. I don't want to speculate what that sounds like. It isn't a very good chord; the "C" and "D" tones will not make for a chord.

The circuit is straightforward, and the horns are ordinary 12 volt horns. The fuse is a 30 Amp circuit breaker in the LH Maxifuse block, which is under the hood on the driver's side behind the air cleaner. The horn relay is in the same place; the engine compartment micro relay center, which is under the same cover as the Masifuse block.

If you had the horns go out one at a time and you have replaced the horns, it is probably the relay or the wiring between the horn relay and the horns.

The circuit breaker is marked the Seat circuit breaker. I believe that you have already checked this and the horn relay. Don't assume that switching the horn relay with another relay verifies unequivocally that the horn relay is good.

DIRECT HORN CHECK

stefank has asked you to do this. Wear ear plugs. Connect 12 volts directly to the horn and see if it sounds. Make sure that they are "A" note and "F" note.

Circuit Checks

If you have a volt meter or a jumper with a 12 volt lamp in it, you can perform checks at the relay socket as follows. Use one of these procedures depending on what you have to do the testing.

VOLT METER

Pull the horn relay.

Check for 12 volts at the red wires, terminals A4 and A6. If there is no power here, check the circuit breaker.

With the horns connected, check for ground continuity (0 volts, or less than 20 ohms) from terminal B6. If you don't see low resistance, either the horns or the wiring is bad; continue checking as below to determine which.

Put the horn relay back. At terminal B4, if you can get to it, you should see voltage with the key on, and it should drop to zero with the key off. You should be able to hear the horn relay click when the horn button is pushed (unless the horns are sounding, of course). If you can't hear the relay click, either the contacts are dirty, the horn button wiring is bad, or the relay is bad; my money would be on the relay, particularly if the car has spent a lot of time in New York.

Do the following for each horn:

Check the resistance between the terminals on each horn. If it isn't low (under 10 ohms), the horn is probably bad. The resistance between the horn connector terminal with the black wire and ground should measure zero ohms; if not the black wire or horn ground connection is bad.

Put the horn relay back, and put the volt meter on one of the green wire terminals at the horn connector. Wear ear plugs if either horn is plugged in. Have someone push the horn button. The voltmeter should jump from 0 Volts to 12 Volts. If it does jump to 12 volts and the horn is plugged in and doesn't sound, look at the voltage on the terminal that hooks to the black wire. If that voltage jumps above a quarter volt or so, the ground wire or ground is bad. If that never moves, look at the connector. Have you friend hold the horn button down while you wiggle the connector and push it onto the horn. If that doesn't do it, the horn is bad.

If the voltage does not go up to 12 volts for either horn, the relay is probably bad. If it goes up for one circuit and not the other, I would look at the wiring for both horns.

JUMPER WITH BULB

Pull the horn relay.

With one end of the jumper clipped to a good engine or chassis ground, touch terminals A4 and A6. The bulb should light. If not, look at the Seats circuit breaker.

Connect one end of the jumper to 12 volts (I don't have a Maxifuse block in front of me so I can't identify a place for you; you may use a 12 volt lantern battery -- or your boat battery -- with its negative terminal hooked to chassis ground if you like). When you touch the other terminal to B6, the bulb should light if either horn is plugged in. Try it for each horn individually. When the bulb doesn't light for a horn, then either the wiring or the horn is bad; check as below to determine which.

Put the horn relay back in. Have a friend push the horn button repeatedly. If you can hear the horn relay clicking, it is probably good, but the horn button circuitry is certainly good.

With one end of the jumper at 12 volts, the bulb should light when the other connector is touched to the horn connecter terminal for the black wire. If not, the black wire, which goes to ground, is bad -- or the ground connection is bad.

Down by each horn, connect one end of your jumper to a good chassis ground. Connect the other to the green terminal at the horn connector. Have your friend press the horn button. If the bulb lights, the horn or connector is bad. Clean the connector and make sure that the wires are making good connection with the brass connectors. Wear ear plugs, and try pushing the connector on the horn and wiggling it while pressing it on. If that doesn't do it, your horn is probably bad.

[KenD]

Good Lord. Now that's concise! WOW!

Thank you soooo much!!!!

Ken