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Horn Just Won't "Shut Up"!

My 2000 Buick Century 3.1 L wouldn’t start, just the clicking. I was able to jump start it. The battery has been in the car 58 months, I do believe it is supposed to last 70 months. So I was trying to check for a parasitic draw with an ammeter, and in fiddling around with the probes and the battery cable, my horn sounded and wouldn’t quit until I opened the horn circuit. I left the battery disconnected overnight while I recharged it. I was hoping that would reset something that maybe needed to be reset to silence the horn. It didn’t. I decided to stop looking for a parasitic load and see about my stuck horn. The battery didn’t hold the charge, yet I was still able to jump start the car. I saw no reason the horn switch would be bad, I hadn’t used it when the horn got stuck. Still, I operated it several times to see if that would free it if for some reason it had failed, made no difference of course. The horn relay is the same type as the A/C clutch relay, which was working fine to control the A/C clutch, so I tried it in the horn relay socket, but the horn still is honking steady. If it is a problem with the manual alarm system, I would think it would be honking intermittently as it is supposed to, and should be able to be reset by turning the ignition key to “run” or it should time out after 2 minutes, per owner’s manual. It does none of these. Might anyone have any ideas as to what else could be wrong here? Like maybe a module, logic circuit or God forbid, even the main computer got goofed up somehow, making my horn stick? Yet nothing else in the car seems faulty.

The horn is usually activated by the horn switch, in the steering wheel, by making a connection to ground which activates the horn relay. The relay then applies power to the horns.
There may be a problem within the wiring going to the steering wheel roller wiring. Hopefully there is a connector near the steering column that you can disconnect in order to isolate the horn switch wiring and prove the problem is there. If you are able to isolate the horn switch and the horn still keeps sounding then you need to look for a ground problem on the wire going to the horn relay coil beyond the steering wheel wiring. The engine computer has nothing to do with this problem.

Get the horn blaring.

Turn the ignition switch on, turn the steering wheel back and forth lock to lock.

If the horn stops blaring, the problem is with the horn switch in the multi-function switch.

image

The horn switch is the copper button on the right.

Tester

Thanks for replies, Tester and Cougar. As soon as I can, I plan to do the steering wheel horn switch check turning the wheel from stop to stop even though I don’t see how it could fail, without sticking after an operation of it, which it didn’t. Also, on my 2000 Buick Century, there are 2 horn buttons in the steering wheel airbag cover, one on either side of the airbag cover; i’m wondering how the horn switch in the multifunction switch ties in with the 2 rotating airbag cover buttons. Is it part of a security system where this switch is only energized if someone is able to somehow start the car in theft, so when they turn the steering wheel it sounds the horn steadily? If the lock to lock test fails, I will also try to find out how to disconnect the horn switch even though it would seem most likely the horn coming on and staying on right as I kept making and breaking the connection from the battery to the battery cable with the ammeter probes when I just couldn’t hold the cable and the probes steady enough to get a steady continuity, somehow led to this problem.

Tester, I spun the steering wheel from stop to stop with a test light in place of the horn, but it didn't cause the light to go out. But it was odd, the light didnt come on when I hooked it up to the horn plug in place of the horn. Seeing the light not on could make it seem that whatever was causing the horn to stick had gotten freed somehow, but the light came back on when I opened the car door to operate the horn switch, then it failed the stop to stop test. I don't want to belabor this issue I'm having by mentioning all these things,  yet I'm thinking you might find it interesting that it is such an odd problem. And I appreciate your advise. 
Cougar, I would like to remove my underhood fuse box and look for a ground fault in the coil control circuit wiring, maybe all the jogging of the battery voltage last week caused arcing & fusing in the circuit board? I couldn't find anything on youtube about how to do it, might you know what all is involved? That seems to me more likely where the problem may be than in the horn switches on the airbag. I thank you for your advice also.

Tester, also, is the copper button on the multifunction switch a spring loaded button that the horn switch rotating contact ring contacts?

It seems the courtesy lights circuit may be involved with this issue since opening the door caused the test light to turn on. Those lights are usually turned on by making a ground connection also, like the horns are.

I would try to isolate the steering wheel wiring as my first test to see if the problem is in that area.

Thanks for this reply also, Cougar. I haven’t given up on wanting to look for the cause of this trouble, but meanwhile I did wire in an isolated horn circuit drawing power right from the battery. I mounted a fused horn button switch close and easily visible on the dashboard to operate a universal relay along with a 15 amp fuse which is the amperage of the the original circuit fuse, to power my existing horns. If I ever find out what’s wrong with the original circuit and it gets fixed, I can use this new circuit to power a novelty horn.

@gudenteit. I did this same ‘fix’ on my 1950 Chevrolet pickup truck. The owner/operators of the school buses I rode did the same repair. One bus was on a 1939 GMC chassis and the other bus was on a 1946 Chevrolet chassis. I am glad to know that horn switch problems are still alive and well at General Motors.

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