[Cloud9...68]

Like it says in the subject line, as long as the horn relay is connected, the horn in my 968 won't turn off.  It started turning on intermittently, reminiscent of the VW van in Little Miss Sunshine (Little Miss Porsche?...), so I replaced the horn relay, and now it's on all the time.  The car has a Momo racing wheel, so no airbag (yes, I placed a resistor to trick the system in to thinking the air bag is still there), and I've completely unplugged the horn switch, and it still blares as long as the horn relay is in place.  If I have the relay i place with the battery disconnected, I can hear the relay click as soon as I re-connect the battery.  I assume the problem was somehow caused by something I did during the install of the Momo wheel, but the problem didn't start immediately afterwards.  There must be a dead short between the battery and the horn, which in principle makes it a straightforward problem to troubleshoot, but it's crazy hot in the garage, so any leads on this problem from someone who has seen something similar would be much appreciated.  Thanks.

 

Edit:  Just a bit of clarification:  As I said, I can hear the horn relay click closed as soon as I connect the battery, but of course the horn doesn't go off until I turn the key to the accessory position.  And I confirmed that the horn button is definitely disconnected.  So the system is acting as though the wiring for the horn button is shorted somehow.  

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[J.Elenbaas]

Is it a possibility that the alarm system is triggering the horn?

Sometimes my horn starts intermittently out of the blue, when i switch off the alarm it stops again.

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[Cloud9...68]

I don't think so - the problem is that I can hear the relay click closed as soon as I connect the battery (it's a streetable track car, with a tiny lithium ion battery, which I disconnect whenever I'm not driving the car).  Then, with the relay activated, the horn starts blaring as soon as I turn the key to the On position.  It's acting as though there is a short in the wiring for the horn switch, because I have the switch itself totally disconnected.  I'm going to lift up the fuse box and start tracing the wires back from the horn relay, and pray they don't descend into the abyss behind the firewall before I can spot signs of a short in one of them.

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[Cloud9...68]

Happy Fourth, everyone.  I have a very small, quick favor to ask of someone.  It's been so long since my horn has worked (and I don't use it much, anyway), that i don't remember if the key has to be in the On position for  the horn to work.  Could someone please check and reply back?  My car is acting like it does, because I can hear the horn relay click closed as soon as I connect the battery, but the horn doesn't start blaring until I turn the key.  This seems odd, though - I wouldn't think the key needs to be turned to activate the horn.  Thanks.

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[MCL968]

Happy Fourth, everyone.  I have a very small, quick favor to ask of someone.  It's been so long since my horn has worked (and I don't use it much, anyway), that i don't remember if the key has to be in the On position for  the horn to work.  Could someone please check and reply back?  My car is acting like it does, because I can hear the horn relay click closed as soon as I connect the battery, but the horn doesn't start blaring until I turn the key.  This seems odd, though - I wouldn't think the key needs to be turned to activate the horn.  Thanks.

 

An answer to a question I had never asked! But, on my 92 the horn DOES NOT honk with the key off and out of the switch.

 

Who knew?

 

Matt

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[Cloud9...68]

Thanks, Matt.  Yeah, that is surprising, and weird, but consistent with my belief that I have a short somewhere close to my horn switch.  So there must be two connected circuits that both have to be active for the horn to blare.  The first curcuit encompasses the battery, horn relay, and horn switch.  The second contains the ignition switch, and the horns themselves.  The first circuit seems to be able to operate independently of the second, because I can get the horn relay to close just by connecting the battery (and assuming my horn switch is somehow shorted).  For a car with a working horn, I would assume that the relay closes when the horn button is depressed.

 

It's similar with the lights, in that the ignition has to be on for them to turn on, but that at least makes sense, because it prevents you from leaving the lights on accidentally after leaving the car.  I don't understand the logic of the key having to be on for the horn to work, though.

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[lbpesq]

If you car isn't running, there is no good reason to honk!


hehehehe

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[Cloud9...68]

I just tested two of our other cars (one American, on Japanese), and both horns work without the key.  Maybe it's a German thing.  I would think that in case someone is attacked or under some other type of distress before they are able to start their car, it would be good if they were able to honk the horn to deter the attacker or draw attention.

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[Waylander]

It might be a duff ignition switch, these cars do odd things with a worn out switch

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[Cloud9...68]

Well, I went in search of a source of the short, so I removed the hub adapter to have a look at the wiper connector and to get a closer look at the wires.  Everything visually looks fine, with no sign of frayed insulation, pinched wires, burn marks, etc.  So I put the hub adapter back on, and on a whim, tested it again.  Everything works perfectly now!  The horn relay no longer clicks shut when I connect the battery, so the horn doesn't go off as soon as I turn the key, and the horn does work when I connect the hot lead to ground, just like it's supposed to.  So it's good that I should be able to pass inspection now, and that I have a working horn, but I sure wish I had identified the root cause, because there's nothing to prevent the problem from recurring, drawing the ire of my fellow motorists.

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[MCL968]

Good, but strange news. I have seen the little metal spade that connects the button to the horn wire get bent and short out on occasion. Is it possible in the process of removing the button you bent the connecting tab and eliminated the short?

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