Curious horn malfunction - PeachParts Mercedes-Benz Forum

strelnik · #1 11-21-2012, 09:43 AM

There are no threads on this at all ( I checked) so here goes with a problem on the 1983 240D:

I tooted the horn a little long today to stop a dog from running in front of my car, and I noticed that i must have blown the fuse.

The turn signals and the horn went out.

I got to work, pulled the appropriate fuse and replaced it with another 8 Amp spare that I keep in the glove-box (I have spares for all three).

The turn signal ligts worked immediately, everything worked but the horn.

Could I have destroyed the horn relay so easily?

Did I forget something simple?

A check of all other fuses showed nothoing bad. I cleaned the contacts where I put the new fuse, too.

Suggestions?

JamesDean · #2 11-21-2012, 09:47 AM

The horn could have died, pulled current on the way out and blew the fuse..and now its just dead?

qwerty · #3 11-21-2012, 10:42 AM

Quote:

Originally Posted by strelnik

Could I have destroyed the horn relay so easily?

Unless your car has been modified, there is no horn relay.

You should have two horns. Perhaps you should check for power at the horn terminals. Or power each horn directly see if either actually works.

JamesDean · #4 11-21-2012, 10:44 AM

I would put meter on the horns input terminals. IIRC one is 12V constant and one is switched ground.

qwerty · #5 11-21-2012, 10:46 AM

Quote:

Originally Posted by JamesDean

IIRC one is 12V constant and one is switched ground.

No.

JamesDean · #6 11-21-2012, 10:54 AM

Quote:

Originally Posted by qwerty

No.

Otherway around then. Switched 12V. Constant ground.

Thats right. Explains why I remember adding a relay to the keyless entry installs for the horn circuit.

mgburg · #7 11-21-2012, 10:56 AM

Pull each horn's terminals and being careful NOT to short either to ground or each other, attach a Volt/Ohm meter (set to Volts in the 20V Range [or better]), then position said meter that you can view it from the driver's position and (Important part here...) with the car NOT RUNNING, try to toot the horn.

If the meter deflects in the proper direction (if not, reverse the leads), then the horn itself is kaputz.

If nothing happens, recheck your connections and try again.

If STILL nothing happens, then you get to trace the wiring for either a burnt lead or you're looking at another fuse situation...like checking the fuse block for the horn's lead, switch (the button/pad on the steering wheel) or the leads to and from the pad itself.

Happy tracing.