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Horn only works when car off


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2002 Boxster S

I had my entire dash out last week (long story). It is all put together now, but now the horn only works when the car is off. If the car is on, it doesn't work at all.

Any ideas? I made sure that the little plugs right behind the airbag and wheel are connected properly.

I didn't notice it for a day or so, but now needs fixed.

Thanks,

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Hi

Is it not possible that you can find the solution for the ABS light problem and the horn problem in the dashbord removal-replacement job?

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The ABS light happened a week after the horn problem, but yes, I assume "something" happened. The dash is not a complicated job, just time consuming. There are not many wires that are disconnected, and each of those plugs were put back in properly.

If the horn didn't work at all, I would understand it. But I can put the key in and out (not touching anything else), and the horn will only work if the key is out of the ignition. That is very weird to me.

Does the horn work normally if the key is out?

Hi

Is it not possible that you can find the solution for the ABS light problem and the horn problem in the dashbord removal-replacement job?

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cheetah

Do you have a spare ignition switch to give it a try? It is a strange problem and difficult to give a solution on the Internet.

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  • 4 weeks later...
Nope, I ju8st bought the car last month. It did not have the problem until after the wheel was off though. But I double checked and the wiring looks correct. RRRR..... :)

I just replaced my 4spoke with a 3spoke and I have the same problem...

Did you find a solution? The wiring seems correct and it looks like it could only even go on one way. This is WEIRD!

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I bought the Diametric tool, and that cleared the airbag and ABS lights.

But the horn still doesn't work right. It is only two wires. They can't be mixed up. Something weird is happening...

Anyone with any ideas?

Nope, I ju8st bought the car last month. It did not have the problem until after the wheel was off though. But I double checked and the wiring looks correct. RRRR..... :)

I just replaced my 4spoke with a 3spoke and I have the same problem...

Did you find a solution? The wiring seems correct and it looks like it could only even go on one way. This is WEIRD!

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This is my mesage on Rennlist after I spoke to 2 mechanics. http://forums.rennlist.com/rennforums/show...ad.php?t=371594

For Cheeta I told Peter that you had pulled the dash. He said there were some ground wires that might had not been hooked up. Sorry, but I was not paying attention. Because my focus was on Gator's simple problem. He swapped a 4 spoke for a 3 spoke steering wheel.

The other mechanic, Manny, said maybe the ignition switch. This I do not understand because when you push on the air bag you close a ground circuit for the horn.

I have done this swap several times over the years on local cars, including my own. I have removed and replaced many steering wheels over the years for the OBC retrofit. Never a problem.

Doug on Rennlist said it might be the "floating ground" deal. I don't know. But Peter told me the same thing might happen if the air bag ground connector is not seated properly. The ground for the horn plate goes away when the ignition is turned on.

So this will be a mystery until someone figures out what is going on.

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  • 1 month later...

Did anyone find out what caused the horn to only work when the car is off? This recently happened to my 2001 Boxster and I am searching for a fix. I recently replaced the ignition switch and I don't know if this caused it or not. Thanks for any help.

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Been Boxstering for 8 years and have never seen this problem on the message boards.

Now, there are 3 cars with the same problem. No one has posted a fix. Still a mystery.

Did you replace the switch because of the horn, or just because of the usual electrical problems with the switch and/or the key sticking. Did your horn work properly with the old switch. Who makes your replacement switch.

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I replaced the switch because of the usual problems, key sticking, accessories not shutting off. The horn worked properly with the old switch and I think it worked with the new switch after it was replaced. I replaced the switch a couple months ago and just noticed the horn malfunction today. I do recall another time I blew the horn with the car running and nothing happened, about a week ago. After I shut the car off, I checked the horn and of course it worked. I didn't think about it again until it happened again today. I checked the switch and it appears to be tight and connected properly. The new switch is an audi switch. I was going to uninstall and reinstall the switch and also look for loose or disconnected wires under the dash. I was also going to try a different relay for the horn and see if there is any difference. I read all the posts on this subject and it has me baffled too. It doesn't make any sense that the ground for the horn would be disturbed by the ignition being on. I searched for more info on the "floating ground" problem mentioned in one of the posts, but couldn't find anything more about it. If I figure it out, I will post the fix, for sure.

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This morning I removed the ignition switch from under the dashboard and while the switch was still connected to the harness, I turned it to the "on" position with a screwdriver and the horn worked. I reinstalled the switch in the dash and when I turned t to the "on" position with the key, the horn did not work. I have a known good switch, so I replaced the ignition switch with the known good unit and again, before the switch was put up under the dash, the horn worked when I turned the switch to "on" with a screwdriver. When I mounted the switch under the dash and turned the key to the "on" position, again no horn. Does the key do something to the switch other than turn it to the "on" position? I made sure the switch was mounted tight against the tumbler mechanism and that the connections were all tight. I also tried a different relay in the No. 10 position with no luck. Any ideas on what to try next?

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This morning I removed the ignition switch from under the dashboard and while the switch was still connected to the harness, I turned it to the "on" position with a screwdriver and the horn worked. I reinstalled the switch in the dash and when I turned t to the "on" position with the key, the horn did not work. I have a known good switch, so I replaced the ignition switch with the known good unit and again, before the switch was put up under the dash, the horn worked when I turned the switch to "on" with a screwdriver. When I mounted the switch under the dash and turned the key to the "on" position, again no horn. Does the key do something to the switch other than turn it to the "on" position? I made sure the switch was mounted tight against the tumbler mechanism and that the connections were all tight. I also tried a different relay in the No. 10 position with no luck. Any ideas on what to try next?

Linklaw:

Do you think the cause of the horn not working when you mount the switch related to the "grounding" of the switch when it is mounted? If so, is there a way to isolate the switch so that it does not get grounded when it is mounted? If you can though, I don't know what that would do, if anything, to the rest of the functions of the ignition switch. Just an idea.

Regards, Maurice.

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Thanks for the idea Maurice, but I don't think the switch is grounded, as it is a plastic bodied device with no exposed metal once it is plugged into the harness. I think I will check the airbag ground as suggested in another post.

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I imagine the wiring to the switch is correct as no work has been done on the harness and the horn previously worked. Also, it works when the ignition switch is turned with a screwdriver to the "on" position before the switch is put into the dash. I will keep working on it and will post the result.

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I must be missing something. My ignition switch plugs into the wiring harness and then is secured to the backside of the dashboard where it mates up with the key/lock mechanism. I assumed there was no wiring to the key/lock mechanism as I did not see any when I was removing and replacing the ignition switch. I see from the wiring diagram that the key closes a contact when inserted. There is a small button in the slot in the ignition switch that is depressed when the key is inserted and I assumed this is the button that would close the contact. Is there wiring to the key/lock mechanism or only to the ignition switch? Thanks

Edited by linklaw
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