The Stovebolt Site Forums The Shop Area The Electrical Bay Horn meltdown

52 GMC, changed to 12 volt, still using 6 volt horn. Rewired using Chevy Duty wiring harness. 52 GMC's did not have a horn relay. Now when I push the horn button the the spring loaded contact in the steering wheel has a meltdown. The spring inside the contact gets very hot and and loses all its temper. The plastic housing of the contact got so hot it started to melt. This was only after two very short beeps.

Do I need to run a horn relay with the Chevy Duty wiring harness? Do I need to reduce the voltage to the horn contact in the steering wheel? There is only wire going to the horn button and two wires to the horn.

Any help is appreciated.

That wire is going straight to ground and it appears to be unfused.

Better get your voltmeter out and trace that wire out and find out where it goes, because it ain't going where it's supposed to.

Hard to imagine no horn relay was used. The horns draw significant current, hence the need for a relay. I'd put one in, and put a fuse in the supply to the relay.

If you're frying your contacts, you have too much current flow, not voltage. Running a 12 volt horn on 6 volts will not increase the current flow. Problems could be a bad ground the columnn to body. Also a bad connection, maybe the contacts in the horn. Also, check the wire size going to the horn and from the horn to the button. It needs to be either 10 or 12 gauge, I'm at work and can't recall which. Adding a relay into the circuit makes sense, I would assume that is how the harness you installed is set up, and using the wiring that is to power the relay (16 gauge?) for the horn could be the problem.

I put a 20 amp fuse inline to the horn and it didn't blow the fuse when I honked the horn without using the horn contact button.

But, when I tried it with the horn contact button in the steering wheel, the contact button had the same meltdown but the fuse didn't blow. I also used a jumper wire from the steering column to a good ground and that didn't help.

All wires are going to where they are supposed to and there is no provision in the Chevy Duty wiring harness for a horn relay and the truck did not have one originally.

The horn spring meltdowns occur because on the AD design trucks many do not use horn relays. There is power to both sides of the horn and it grounds at the steering wheel. Many horn contacts in the steering wheel purchased thru suppliers only have the contact with a small spring in it without the braided wire that it needs to carry the extra voltage. Thus the small spring melts inside the horn contact case. I took apart a contact purchased from Jim Carter and soldered my own wire inside. Everything works fine.

I'd strongly reccomend adding a horn relay! Tha last thing you need is a potential meltdown up through the steering shaft!
Jerry

SoTxBoTi, 53 was the first year for the horn relay on the ADs. And, also the first year for the seashell horn as a standard option.

Any one know where a schematic is avalable for a 1953?? This should show how the relaly is wired in and would the horn relay be avalable today and is it completely compatable with the old style horns???
Denny Graham
Sandwich, IL

Wiring diagrams

http://chevy.oldcarmanualproject.com/electrical/wiring/pdf/53truck.pdf

http://chevy.oldcarmanualproject.com/electrical/wiring/images/53csn1112.jpg

regards,
Leon

Thanks Leon, I figured Keith would have something on his site.
looks pretty simple, pulling B+ off of the regulator I assume the relaly would be mounted close to it. Now, I just need to find out if the 6v automotive relays are still avalable. I would think the new SS relalys are all wired for 12v.
I never did like the idea of running all of that current through the slipper contact.
Denny Graham
Sandwich, IL

Denny, the relays are available from the vendors. Prior to 53 the horns had two lugs, the 53 seashell has one lug. Here is a pic (not so good) of where the relay mounts... looking at the pic it is the small box to the left of the fuse box.

[IMG]http://thumb1.webshots.net/s/thumb3/1/29/90/122012990NzggSQ_th.jpg[/IMG]

Nice job on the '53 Ron, only wish I could down load the pix from Webshots for my reference file. The picture shows the location just fine.
I'll check through the catalogs and see what they have listed.
I doubt if I ever showed the truck that any one would notice that it had a relay added.
Yes, the horn is hot all the time and the button just completes the ground on my '50. The horn on the '53 is grounded and the relay is feeding it B+ when it's energized. Looks pretty simple and a lot safer setup also.
Thanks
Denny G