Author Topic: Horn problem with my 230  (Read 2117 times)

Slowwindow805

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Horn problem with my 230
« on: March 25, 2021, 18:55:01 »
I have just finished rebuilding my power steering pump and was going to start the car to check for leaks but the horns came on when I turned the ignition on.  I didn’t do anything to the horns like remove a wire since I took the pump out through the front after removing the radiator.  I know there is no relay on these cars but how do you test the circuit while horns are blaring in your ears, I removed the fuse to run the car but would like to fix the problem if possible.  Any ideas? Thanks

Cees Klumper

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Re: Horn problem with my 230
« Reply #1 on: March 25, 2021, 19:50:18 »
If it were my car, I would disconnect the horns, attach a test light in their place, and then turn on ignition and start troubleshooting. Sounds like somehow a short in whatever wire makes them blare, but I am far from an electrical 'knowledgeable'.
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

Slowwindow805

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Re: Horn problem with my 230
« Reply #2 on: March 25, 2021, 22:59:36 »
That’s good advice thanks

Pawel66

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Re: Horn problem with my 230
« Reply #3 on: March 25, 2021, 23:29:44 »
I would go as Cees suggested. As for potential places to look for it seems some wire was squeezed between pump bracket elements or maybe (I had something like that in W463 with different type of connectors in the steering wheel, but who knows...) when you were working in the front, you turned the wheels by hand, which caused steering wheel to spin very fast and damaging the contact brushes or their wires. Just speculating...
Pawel

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66andBlue

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Re: Horn problem with my 230
« Reply #4 on: March 25, 2021, 23:51:09 »
Did you take the steering wheel off perhaps?
The wire to the horns will be hot when you turn the ignition on but not connected to ground. That connection is established by the horn switch on the steering wheel.
Looks like you have a short that connects the horns to ground.
Alfred
1964 230SL manual 4-speed 568H signal red
1966 230SL automatic 334G light blue (sold)
1968 280SL automatic (now 904G midnight blue)

lpeterssen

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Re: Horn problem with my 230
« Reply #5 on: March 26, 2021, 11:39:04 »
Exactly Alfred explanation is the most accurate.

Horns circuit is hot every time ignition is on the RUN/ON position. So the cable black/yellow gets energized then. The circuit is completed each time you press the horn button giving the GROUND needed to make them sound.

As suggested by previous members disconnect the horns cables going to the horns itself.  In some models is just a spade female connector, on others is a “O” shaped connector. Tape the cable black/yellow which is powered. And start your circuit testing by confirming that there is a ground signal on the cable black/yellow/pink by doing a continuity test to any chassis part of your car.

As asked by Alfred your horn ring behind the steering wheel may be defective or been in the wrong position since is closing to ground all the time. I would remove the steering wheel and disconnect the horn oring switch from ground and see if the horns still receive ground at their terminals. If ground signal is no longer at horns once removed the steering horn ring switch, then your problem is there. If horns still have ground after this, the problem is Elsewhere on the wiring harness.

Study carefully the switch outside the car, see if it’s well assembled and test its switching function with a multimeter.

Have fun with your electrical criminal investigations and find the culprit for the self activating horns....

Best regards
Lpeterssen

Slowwindow805

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Re: Horn problem with my 230
« Reply #6 on: March 26, 2021, 14:33:43 »
Thanks very much, I feel ready now to find the problem with your information