Horn works with Engine off but not When running

[wbailey2112]

My horn has stopped working when my engine is running. Works fine when it’s not. Could it be the voltage regulator that’s the issue? Looking for some ideas on what it could be. Thanks!
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'74 Thing
'83 Westfalia

[dlicious]

Just for clarity, this happened recently? or has it always been like this for you?
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'63 Caravelle Camper
dLk

[wbailey2112]

Just started recently.
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'74 Thing
'83 Westfalia

[dlicious]

looking at the wiring diagram....Its the second from the left fuse. That fuse also controls your brake lights. Take it out and check it. clean the contacts. See what your brake lights do with the key off and on.
It is a simple circuit, there isn't a lot tied into it.
There is a ground wire located at the steering coupler that needs to be looked at too. Thats how the horn completes the circuit. It would seem with the car off the horn circuit is shorted out and going along a 'live' circuit (thats dead with the car off) and grounding somewhere else.
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'63 Caravelle Camper
dLk

[dlicious]

The wiring diagram is located in the technical tab at the top. Click that then Wiring then change selection to Thing.
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'63 Caravelle Camper
dLk

[wbailey2112]

Not a fuse issue or it would not work at all. Not the ground circuit or the ground strap at the bottom of the steering column since if the ground loop was broken again it would not work at all. It must be something to do with it being powered by just the battery vs being powered by the generator when it is running.
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'74 Thing
'83 Westfalia

[wbailey2112]

Still at a loss on this one. Replaced the ignition switch this weekend and still doesn’t work with the key turned to the on position. I’m stumped.
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'74 Thing
'83 Westfalia

[mondshine]

The horn should not work at all with the ignition switched off.

The black/yellow wire should carry battery voltage when the ignition is switched on. Test it at the horn with your VOM.

If battery voltage is present at the horn, momentarily ground the other horn terminal. If the horn sounds, the problem is in the ground circuit.

It is possible that the plug at the steering column switch is plugged in "out of register"; that it was not correctly aligned when it was pushed on.

So check those 2 plugs on the steering column.

Old photo:

Good luck, Mondshine

[wbailey2112]

Well the mystery has been solved and it was a very simple fix that I had just overlooked. Before I share the solution though and in the interest of full disclosure I need to share that the previous owner of my Thing replaced the stock wiring harness with a Ron Francis Bare Bonz VW wiring harness and fuse panel so troubleshooting based on the standard VW Thing wiring harness really did not apply here...at least not for everything.

Over the weekend I had to jack up the front end to grease the front beam. While I had it up I decided to check the ground jumper on the steering coupler. There I found that it was broken at one of the connectors. Made up a new one with my trusty Super Champs and now the horn works whether the ignition is turned on or off.

My guess is that the locking pin in the steering column was providing an alternate path to ground when the ignition was turned off. When it was turned on the pin retracted and this alternate path to ground was broken.

Lesson learned is always check the most commonly known causes first (like this notorious ground jumper on the steering coupler) before looking for other possible causes.
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'74 Thing
'83 Westfalia

[mondshine]

[Dougster43]

I had to run a ground strap from the body to my steering box as well. I had everything including the front beam powder coated as part of the restoration and the steering box was no longer grounded. Once that was in place the horn worked perfectly.

[mondshine]

Just one more little detail...
The black/yellow wire that powers the horn should only be "live" when the ignition is switched on, and not with the key out.
So make sure it is connected to the correct fuse (#2 from the left).

Good luck, Mondshine