Horn Problem

jcode68 · Jun 26, 2010

So I finally have some time to get the Stang inspected so I can start enjoying it for the summer and the dang horn doesn't work. So I go back home and start to troubleshoot. Here's what I have found:

I jumped a wire from the + battery to the horn and it works no problem.
I removed the horn pad from the steering wheel (stock 68 wheel) and when I press the horn, it makes contacts and throws sparks. It also seems to be heating up the wiring harness that connects to the steering wheel fo rthe horn and directional. So I'm thinking there is a short circuit somewhere?
I checked all the connectors to make sure they were tight etc, can't see any stripped insulation or where it would be shorting out.

I am not very good with electrical circuits, so I'm not sure how to troubleshoot this problem. The fact that I get spark when I press the horn tells me I am getting power, so I don't think there is a blown fuse preventing power to the circuit. How do I troubleshoot this problem? I did a forum search but didn't find anything that helped too much. I have the service manual, looked at the horn circuit and have identified all the wires involved, however nothing obvious jumps out at me. Thanks for quick responses, I want to drive my car today!

2+2GT · Jun 26, 2010

Try checking to see if the connectors between the steering column, firewall, etc., have power. You may only need to clean some corrosion off the pins.

jcode68 · Jun 26, 2010

I disconnected and reconnected the harness and didn't look corroded at all. Given I am getting spark when I ground the horn contact, it seems like I have an open circuit or short.

2+2GT · Jun 26, 2010

jcode68 said:
I disconnected and reconnected the harness and didn't look corroded at all. Given I am getting spark when I ground the horn contact, it seems like I have an open circuit or short.

If you mean you depress the horn ring, and the contacts spark, but horn does not sound, this is fairly normal. If the horns are a bit "off" adjustment, and the engine is not running, the bad adjustment and low voltage will combine to prevent the horn blowing. Remember, the battery is 12V, but the car runs on 14V.

jcode68 · Jun 26, 2010

I know a small spark at the contact points is normal since it is actively grounding and closing the circuit, but this shoots a pretty sizable spark and not just from the contact points, but also from the main power feed going to the horn ring. Plus the wires get real hot after pressing it a few times. When I direct connected the horn to the battery at 12 volts, plus I tried it with the car running and nor a peep. Appreciate the feedback, keep the suggestions coming.

2+2GT · Jun 26, 2010

OK, disconnect both horns. Depress the horn. You should get no spark at all. If you do, the horn lead is grounded somewhere.

Tim65GT · Jun 26, 2010

If you are heating up the wires that indicates a short to ground. Look at the blue-yellow switch output wire. With it disconnected at the horns, Use a meter and check for ohms to ground on that wire and then disconnect the firewall connector and then the column connector. Maybe you can isolate in what harness it is shorted and run a bypass wire in that section.

jcode68 · Jun 27, 2010

Ok, still haven't figured it out, but here is the update:

I disconnect the wires to each horn, push the horn and still see a spark.
I disconnect the steering wheel harness and with my test light, I touch the yellow wire and it lights up. The blue with yellow wire does not light up.
I disconnected the harness that feeds the horns from under the dask, reconnect the steering wheel harness and still have sparks.

I looked everywhere for problematic wires, but don't see any. This is the original wiring harness and it is 100% unmolested and in extremely good condition. That doesn't mean it can't have a problem, but just saying it's not a rats nest of aftermarket wires spliced in everywhere. I'm not very good with a multimeter, so will need some more details on measuring ohms. Appreciate the help guys

jcode68 · Jul 4, 2010

Bump...
I will have some time tomorrow to work on this, looking for any further input on how to isolate. Help is appreciated.

2+2GT · Jul 4, 2010

jcode68 said:
Bump...
I will have some time tomorrow to work on this, looking for any further input on how to isolate. Help is appreciated.

Systematically. Isolate each section.

Start at the under-dash power lead, and assure that it gives power cleanly to the steering column. Then test into, and back out of the column. Once you know that is OK, start working toward the horns, isolating each section.

Tim65GT · Jul 5, 2010

jcode68:
I disconnect the steering wheel harness and with my test light, I touch the yellow wire and it lights up.
The blue with yellow wire does not light up.

You can do troubleshooting without an ohm meter.

See if you can find connector "C". It should be a 4-way plug with the blue-yellow along with a brown, Green-red and red-blue wires somewhere in the engine compartment near the voltage regulator. See what happens when you try it with it disconnected. If it does not spark anymore, the blue-yellow wire is pinched or melted in the front harness somewhere and is touching ground. If no change, reconnect and try next check:

Disconnect the steering column connector (connector "D") and try to jumper the yellow(#460) to the blue-yellow(#482) at the harness end. If the horns work, the blue-yellow wire is pinched or melted in the column and is touching ground (my guess). You will have to pull the wheel and the signal switch to check it out.

If it sparks with the jumper, and no horn sound, the the blue-yellow wire is pinched or melted in the harness and is touching ground somewhere before the "C" connector.

Max Power · Jul 5, 2010

Lotsa good advice here.

I always start at the end and work backwards, meaning I would hook a voltmeter to the plugs the connect to the horns and see if they are getting a full 12v or not. If not, work your way backwards to the source of 12v.

jcode68 · Jul 5, 2010

Appreciate all the great advice guys. Made some progress and have narrowed the problem to the following:

Tim65GT said:
Disconnect the steering column connector (connector "D") and try to jumper the yellow(#460) to the blue-yellow(#482) at the harness end. If the horns work, the blue-yellow wire is pinched or melted in the column and is touching ground (my guess). You will have to pull the wheel and the signal switch to check it out.

If it sparks with the jumper, and no horn sound, the the blue-yellow wire is pinched or melted in the harness and is touching ground somewhere before the "C" connector.

I need to pull the guage cluster to get better access to the wiring harness as it is tucked up under the dash pretty well. Was a little hot to keep going on it this afternoon, maybe in a couple hours when the temps drop a bit I will get back out there and pull the cluster. Will report back when I find the bad connection. Thanks again!

66Couper · Jul 7, 2010

Don't mean to deter you from solving the real problem but if you really want to drive the car in the mean time you could just buy a button at Radio Shack and rewire the horn to a different spot in the interior.

I had a similar issue with mine, so I put the horn at the floor next to the high beam switch.

GL

jcode68 · Jul 13, 2010

Just to put some closure on this post - I was able to resolve the problem. I had to pull the guage cluster in order to access the main harness. Had a short in one spot where the insulation had chafed. Simple fix, bitch to find. Thanks for all the help!

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