No horn when car is moving. Any ideas?

[JP911]

My horn has never worked quite right, so I set about fixing it (trying) today. I replaced the high tone horn and now when the car is sitting still, either without the key in or in the run position, the horn works fine. It's when the car is running (sitting still or moving) that it won't work. I have a Momo wheel and the car had an aftermarket alarm system. Any help would be much appreciated.

[john walker's workshop]

loss of continuity to ground through the old steering u joints probably. try replacing the plastic sleeve inside the top column bearing with the steel one. 928 347 739 02. takes 5 minutes.

[turborat]

According to my wiring diagram (77 not 76)..... The horn power comes from fuse 17 (bottom or battery side). It also shows a jumper between fuse 17 and 18. Fuse 18 powers the clock and interior lamp. Does clock and dome lamp work with engine running? I cannot determine anything that would change the routing of power with engine running. Maybe a mis wire when the alarm was removed as it may have used the factory horns.

[john walker's workshop]

it still has to complete a ground. it can have all the power it wants, and it ain't gonna work unless it can ground through the steering column.

[JP911]

John-
It sounds like you've seen this problem before. What is it that allows the horn to work when the car is not running if the ground is bad? I'm a bit soft on the electrical skills.

[Don Plumley]

Just guessing - with the car running, there is just enough vibration to affect the ground.

[JP911]

Good point. Maybe even the weight of a hand on the wheel. I'll have to experiment further in the AM.

[randywebb]

electricity only works in a closed loop...

[ruf-porsche]

I think you need to slow down if you want to hear the horn, you could be traveling faster than the sound barrier, or the wheels may not be touching GROUND. Do you hear a VARABOOOOM in the back of your car?

[JP911]

And I thought that was just backfiring! These cars really are FAST!

[bkreigsr]

you can't beat my bonehead move of pinching the wires in the momo adapter ring during the install.
horn worked fine for about 2 years then stuck on beeeeep at an autocross. oops. ended up burning out the relay and the two horns.

[JP911]

Update:
I followed John's advice and hammered in the metal steering column bushing. My horn now works in all conditions! And I think my neighbors are glad I'm done fixing/testing it. The aside here is that I never realized how much slop I really had in my steering column;steering feels much tighter now. Thanks much for the advice John!

[kees]

Dear Mr.Walker,

I've got the same problem (no horn when driving). I've checked everything and the only thing I haven't done is replacing the plastic sleeve with the steel one.

I've no problems at all with the steering and the plastic sleeve looks ok (for as far as I can see), but I like to make my horn work.

Can I still replace the plastic sleeve with the steel one or is this not a wise thing to do? If my horn is still not working after replacing is there no harm done?

Thank you very much,
Kees.

[Rot 911]

Originally posted by kees

Can I still replace the plastic sleeve with the steel one or is this not a wise thing to do? If my horn is still not working after replacing is there no harm done?
Thanks you very much,
Kees.

The metal bushing is actually an upgrade. Your plastic bushing will eventually fail. Just get the metal bushing and tap it down over the column. It will push the plastic bushing down where it will do no harm.

[safe]

Originally posted by john walker's workshop
loss of continuity to ground through the old steering u joints probably. try replacing the plastic sleeve inside the top column bearing with the steel one. 928 347 739 02. takes 5 minutes.

Wow, my horns used to worked some of the time when I got the car but suddenly they worked all the time??
Guess what, I have replaced the plastic sleeve
Never connected the two issues!!

[kees]

Originally posted by Kurt V
The metal bushing is actually an upgrade. Your plastic bushing will eventually fail. Just get the metal bushing and tap it down over the column. It will push the plastic bushing down where it will do no harm.

Thank you Kurt, that's exactly what I hoped to hear.

Kees.

[Jeff Higgins]

Whatever happened to "horn broke; watch for finger"?

[kees]

Originally posted by Kurt V
The metal bushing is actually an upgrade. Your plastic bushing will eventually fail. Just get the metal bushing and tap it down over the column. It will push the plastic bushing down where it will do no harm.

I can't get the metal sleeve into position. I think I tapped it pretty hard. I thought it would be an easy fit. I used a piece of PVC pipe to try to tap it in. Do I need to hit it really, really hard?

Thanks,
kees.