Horn problems - electrical

Discussion in 'Workshop Forum' started by EJP, Oct 31, 2019.

  1. EJP

    EJP Low Mileage

    Location:
    Monroeville, PA
    When I bought this '79 X the horn didn't work. Took off the horn button to find no contact springs. Bought 2 from Midwest. Put them in tonite, reattached the horn button, pushed on it twice, heard a couple of what sounded to be relay clicks and blew the fuse. Pulled down the fuse panel from below the glovebox. Took off the horn button and removed the springs.Put in another 16 AMP fuse, attached jumper wire from spring location to horn contact ring and blew that fuse. Put in another fuse, attached the jumper and now get a low pitched squealing sound from the fuse panel under the glovebox. Fuse did not blow. Could it be the relay making this sound? Thinking I may have fried it, I swapped the horn relay with the rear window defrost relay. Look the same. Same Bosch part number on them. Made no difference. No horn. Just this electrical squeal.

    While waiting for the springs to arrive, thought I would do some maint and clean up the rusty grounds in the headlight buckets. The horn did work via jumper wire before I took the grounds apart for cleaning. Is one of these ground wires horn related or does the horn ground itself to the car body? Did these cars only come with one horn on the left side? I have none in the right headlight bucket and maybe some cut wires since no horn there??? I am at a bit of a disadvantage looking at the wires in the headlight buckets as when the previous owner had the car painted, they painted all of wiring as well. The paint does not clean off even with lacquer thinner.
    I do have the interior gutted (center console switches all removed, seats belt buckles, etc). Looking to replace carpet. Is this squealing sound I am hearing a seat belt warning thing since the seat belts wires are just lying on the floor.
    Also, turn signals do not work front or rear. Are any of the grounds related to these lights. They do light up when the headlights are on. Maybe just a bad turn signal relay? Don't know if they ever worked.
    I would really appreciate some advice and thoughts on this horn mystery. What looked like a simple fix has now turned into a larger PITA job. If I did something stupid to cause this, just say it. Dont want to do this again. Sorry for the length of this but wanted all to know what I did.Thanks!
    Ed
     
  2. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    There's a '79 wiring diagram on our wiki: http://xwebforums.com/wiki/images/a/a4/1979_wiring_diagram.pdf

    Painted-over wires and the possibility that the wiring has been modified by previous owners means that wiring diagram may not be a panacea, but it's still a good place to start and will at least tell you how things are supposed to work. And with that said....

    There are supposed to be two horns, one in each bay. I've seen several types of horns, some grounded directly to the chassis through their mounting bolt and others grounded by a separate wire to the chassis. However, the horn grounds are a red herring here - if they aren't working that will stop the horn from sounding but won't a blow a fuse. The same fuse powers both the low amperage current through the horn button that switches the relay and also the high amperage switched current controlled by the relay that blow the horn. The fuse is blowing because the switched wire is shorted to ground somewhere downstream of the relay - a good bet is that the wire to your missing second horn is flopping around in the headlight bay and touching the chassis.

    In any case, you're going to have find and fix that short before you work on anything else. Use a multimeter and look for continuity between the relay output and the chassis (don't keep doing things that blow fuses - the current needed to blow a 16 amp fuse can burn other stuff up).
     
  3. EJP

    EJP Low Mileage

    Location:
    Monroeville, PA
    Eric,
    Thanks for the reply and information. The thing that upsets me is that before I decided to clean up the ground connections in the headlight buckets, everything was working fine.
    Ed
     
  4. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    Good grounds are essential to getting the electricals working reliably, so it's good that you did that - you'd be doing it at some point anyways. However, if it stopped working afterwards, then one way or another you changed something. Possibly the wire that powers the missing horn was just flopping around loose and you moved it around so now it's touching ground? The missing horn is evidence that someone has been messing with the wiring, probably incompetenty, and your goal is to unmess it again, starting by identifying your fuse-blowing short.
     
    kmead likes this.
  5. EJP

    EJP Low Mileage

    Location:
    Monroeville, PA
    Eric,
    Success!!!! Thanks for the responses and guidance. I now have a working horn and turn signals again. Recleaned and reconnected all of the ground contacts again and the horn contacts. I did find an open ground wire buried in the right headlight bucket. Not sure what it is for but it is now connected. Also found the light blue wire that fed the missing horn. Taped it off. All is good. Thanks again
    Ed
     

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