Author Topic: A shocking horn problem!  (Read 4489 times)

mrfatboy

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A shocking horn problem!
« on: October 14, 2005, 16:16:20 »
Sorry to start a new thread but my horn problem has now turned into something different.

Let me start at the beginning. About 4 years ago I was driving down the street when my horn fell off its bracket. I dragged the damn thing with the wires connected to it for 100 yards. I had no tools with me and I was dressed for work. All I could do was cut the wires and throw the horn in the trunk. That weekend I got a bracket and hooked the horn back up. I thought I did it right but I kept blowing the fuse when I used the horn. I thought the horn broke while I dragged it down the street causing the short. I guess not.

Anyway, I got busy and forgot about it. I hooked the wires together so the right horn would work.

Now today, while I was getting back to this project I some how screwed up my wiring that when I honk the horn I get shocked at the horn handle or touching the car. But the right horn works.

Basically, at the left horn there is a pair of wires (from horn handle) that connected to the left horn which are connected to another pair of wires to the right horn. I just connected them together without the left horn. Both pairs are the same color. Black with white stripe.

I just know a little about electricity to get in a lot of trouble. I used my volt/ohm meter to figure out the wiring. Obviously, I screwed it up.

Help, any suggestions?
1969 280sl (Aug 1968 build)
Signal Red
4 Speed

ja17

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Re: A shocking horn problem!
« Reply #1 on: October 14, 2005, 20:33:52 »
Hello mrfatboy,

These horns are wired parallel. So hooking the two wires together would cause a problem. Your other good horn should work with the two wires from the missing horn isolated. The horn ring is basically part of a switch which completes the ground to the horns, so being ground you do not get shocked. When you hooked the two wires together from the missing horn you allow positive voltage to flow back up to the horn ring and you get shocked.

Unhook the two wires and isolate them from each other or re-mount your other horn.

Joe Alexander
Blacklick, Ohio
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

mrfatboy

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Re: A shocking horn problem!
« Reply #2 on: October 14, 2005, 22:38:09 »
I am not hooking the 2 wires together.  There are 2 wires coming down to the left horn. I hook them to the horn. Then there are 2 wires jumping over to the right horn.  Everything should be wired in parrallel. But I still get shocked.

Basically, when i honk the horn, the horn honks and I also get shocked.

I had some rats in my car a while back.  I wonder if they chewed thru some of the wiring and it is shorting under the dash.

Any other ideas?
« Last Edit: October 14, 2005, 22:52:17 by mrfatboy »
1969 280sl (Aug 1968 build)
Signal Red
4 Speed

68_white

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Re: A shocking horn problem!
« Reply #3 on: October 15, 2005, 00:01:01 »
I repaired my horns about a year ago. I had to look up the wiring diagrams in the blue book to figure out the wire connections. Yes, they are connected in parallel. If I understand you correctly, you have both horns wired but only the left horn is working. Also, I understand that you had dragged the right horn and possibly damaged it??  It is possible that if the horn you dragged was damaged then there may be a short inside that horn. I suggest you disconnect the damaged horn. You may want to inspect the insides to see if there is any shorting there.

HARRY

68_WHITE
HARRY

1970 280SL RED
2002 E430 SILVER
1996 911 BLUE

mrfatboy

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Re: A shocking horn problem!
« Reply #4 on: October 15, 2005, 06:02:51 »
Upon further testing it appears that both horns are fine as far as I can tell.  If I hook both up or each one individually the problem is the same (even change positions)---- When I honk, I get shocked! Mind you, the horns are making the correct honking noise when I do this. Originally I thought it was the damaged horn but now I am thinking a rat chewed thru the protected wire coating under the dash (horn wires).  The damage hot wire might be touching the frame or something that it shouldn't.

If that is the case I would think when I honk, the current is flowing to the horn (honking it), but also shorting right back to the horn ring thereby shocking me. Does that sound even possible?  Wouldn't the fuse blow?

Now as I type this I am thinking that if this is truely the case (my short theory), if I disconnect the horns and leave the horns wires isolated and unconnected I would still get shocked when I pressed the horn ring (because of the short under the dash).  I will have to try that in the morning.  

Any other help would be appreciated!

« Last Edit: October 15, 2005, 06:09:57 by mrfatboy »
1969 280sl (Aug 1968 build)
Signal Red
4 Speed

ja17

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Re: A shocking horn problem!
« Reply #5 on: October 15, 2005, 06:24:36 »
Hello,
Take a test light and see if the horn ring is "live" when you depress it. It should not be since it  completes the negative to the horns.  Make sure the battery is not in backwards everything will work except for the fuel gauge. Of coarse the fuel pump would run backwards unless the wires were switched there also. If you had a dead short, the horn fuse should blow. Somehow the polarity to the horn switch is reversed.

Joe Alexander
Blacklick, Ohio
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

mrfatboy

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Re: A shocking horn problem!
« Reply #6 on: October 15, 2005, 12:13:47 »
Horn update.

I have done some more testing.  It seems the main horn wires at the left horn are putting out .5 volt when the horn ring is NOT being press.  Is this normal?  Is this my little short?

When I turn the ignition on the horn chirps for a split second (without pressing) which is wrong.

I am still thinking there is a possible frayed wire under the dash that is connecting to ground just a little bit to produce .5 volt.

Any other suggestions?  I don't want to go under the dash if I don't have to.
1969 280sl (Aug 1968 build)
Signal Red
4 Speed