Horn Problems

[landy]

Still having some horn problems. Now I know why the P.O. must've disconnected the horn.

With 12 volts applied directly to the horn it works. Replaced all the column horn components, grounded the steering wheel button and no horn. So then replaced the horn relay, grounded the horn button and got some buzzing and some smoke. Checked the horn relay and it had a hole burned in the side of it, so I know there's a short in the circuit somewhere, but I'm not sure where to start. I have one horn with a non-original wire running to the terminal The factory wiring diagram seems to indicate that a wire should go from the horn to the fuse panel. Is that correct?

Thanks!

[JimKshortstep4x4]

There are three wires connected to the horn relay, 1 large green which routes from the horn through the fuse panel directly to the relay, 1 large red which is the power wire, and 1 small black wire which comes from the steering column. The small black wire activates the relay and grounds the relay when the horn button is depressed.

If all of the wiring is intact then the green wire would be the wire to cause the short since the relay sends power to it when it is activated. I would disconnect the green wire at both ends and using an ohm meter check the resistance to ground. If resistance is low then a short is indicated. If a ground of the green wire is indicated then check the harness by stripping the tape back and inspect the green wire from the fuse panel to the relay.

If any wires are cobbled in the harness, check those, also. The factory horn wiring is well designed and from what my experience has been it is trouble free.

Jim

[landy]

Looking more closely, I found the non-original wire that goes from the horn through the dash isn't connected to anything, so there's no power to the horn.

To confirm, the green wire from the relay as originally wired should have connected directly to the horn?

[Stocker]

Originally Posted by landy

To confirm, the green wire from the relay as originally wired should have connected directly to the horn?

Yes.

[landy]

Still having horn problems. I've replaced the relay, signal switch, and cancelling cam. When I put the cancelling cam onto the steering shaft and push it down, the bottom brass part of the cancelling cam contacts the edge of the turn signal stalk, grounding out, and the horn goes off.

I'm not clear on how the horn components inside the steering column are supposed to work, so maybe I'm missing a part? But I don't think so, because I've compared the parts diagram in the LMC catalog and the repair manual, and it looks like I've got everything.

I understand that when the barrell shaped copper button is pushed down and grounded the relay/horn is activated. And I'm assuming that the bottom of the cancelling cam shouldn't be contacting anything other than the copper button. There's very little clearance between the brass bottom part of the cancelling cam and the edge of the turn signal stalk - maybe there's a spacer or spring I'm missing? It's a non-tilt column, BTW.

Could I get an explanation of how the horn parts inside the steering column work?

Thanks!

[LSUMurse]

I am definitely not an expert in this area, but could it be a short in the horn itself? Maybe it's shorting inside the horn assembly. Smarter people than me will have to weigh in, just a thought.

[landy]

Well, I'm obviously no expert either, so all suggestions are appreciated. I don't think it's the horn since it works when I apply a direct 12 v source to it. And I think the wiring is ok from the steering column to the horn relay. Perhaps a problem from the relay to the fuse panel to the horn?

I think if I can get a better understanding of how the steering column horn components work, I'll have a better chance of diagnosing the problem.

[Big Daddy 70]

I'm not sure if this will help, but I recently changed my steering wheel, and found I had put the flexible piece in backwards, so it didn't pop back correctly.

I had the following components when I took it apart, in this order:
Horn button
Ring with plastic insert
Flexible piece
Nut/washer

Hope it helps.

[landy]

Man, this horn problem is really bugging me. So without the cancelling cam installed, I installed the steering wheel and the horn starts blaring. In order for the horn relay to be actuated, the copper button must be depressed and the circuit completed by the steering wheel grounding to the steering shaft or something other metallic piece. Can somebody provide an explanation of how the horn and relay circuit work?

Also, my steering wheel seems way to close to the turn signal stalk. Is there supposed to be a spacer somewhere?

Thanks!

[Stocker]

Originally Posted by landy

Can somebody provide an explanation of how the horn and relay circuit work?

How it works is simple -- but obviously getting all the parts together just right is not so easy.

The horn is grounded through the mounting bolt, so it's activated by 12vdc via the green wire, which comes from the horn relay.

The horn relay always has 12vdc on one side of the winding as well as one side of the normally-open contacts. Ground from the horn button operates the relay and extends 12vdc through the contacts to the horn.

Your problem is that the wire is getting grounded at or near the horn button. I don't have anything showing how all the parts fit together so I can't help you there, sorry.

[landy]

The wire grounding at the horn button is puzzling. It's a new turn signal switch which comes complete with new horn button and wiring. I suppose it could be defective or perhaps I could've chafed a wire installing the assembly?

[landy]

Ok, so I removed the new turn signal switch to inspect the wires for any chaffing in the insulation - all looked good. With the turn signal switch removed from the column, the meter shows 12 v between the copper button fully extended and the steering shaft. If the button is pushed in, it shows 12 v also. I think it should only show 12 v when the button is pushed in and grounded to the steering column, correct?

Perhaps the switch is defective? Any other possibilities?

Thanks.

[Stocker]

Originally Posted by landy

I think it should only show 12 v when the button is pushed in and grounded to the steering column, correct?

No -- the 12v you are reading on the copper button sounds normal, and is coming from the horn relay (through the winding). Pressing the horn button should ground that copper button, thereby sending ground to the relay and thus operating the relay.

I may be missing something, but I don't believe the turn signal switch should have anything to do with the horn wiring... unless it's interfering with it, but it passed your inspection....

[LockDoc]

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Here is a thread that I posted some info in. It is kind of long and you really have to read the whole thread before you can get all of the info as it jumps around a little.

http://67-72chevytrucks.com/vboard/s...d.php?t=426902

All of the parts needed are shown in post #20.

LockDoc

[68 P.O.S.]

Here's another old thread on it.

http://67-72chevytrucks.com/vboard/s...d.php?t=229041

[landy]

Without the cancelling cam installed, I put the steering wheel onto the shaft and the back middle steel part of the steering wheel touches the copper button and the horn goes off. So even without pushing the copper button down, which apparently is supposed to send current to the relay, the circut is being completed. There's got to be short somewhere, right?

On a related matter, my steering wheel seems way to close to the upper steel column piece. The back part of the steering wheel is rubbing on the steel column piece. This truck had a small diameter after market steering wheel when I got it, and all the horn components were missing as well. I bought a used 2nd gen steering wheel to replace it with. Is there a spacer of some sort. But if there was, the shaft wouldn't be long enough for the steering wheel to fit onto. Any thoughts?

Thanks!

[landy]

Bump

[LockDoc]

Originally Posted by landy

Without the cancelling cam installed, I put the steering wheel onto the shaft and the back middle steel part of the steering wheel touches the copper button and the horn goes off. So even without pushing the copper button down, which apparently is supposed to send current to the relay, the circut is being completed. There's got to be short somewhere, right?

On a related matter, my steering wheel seems way to close to the upper steel column piece. The back part of the steering wheel is rubbing on the steel column piece. This truck had a small diameter after market steering wheel when I got it, and all the horn components were missing as well. I bought a used 2nd gen steering wheel to replace it with. Is there a spacer of some sort. But if there was, the shaft wouldn't be long enough for the steering wheel to fit onto. Any thoughts?

Thanks!

It is working correctly then. The copper piece is not a button, it is a ground. You are not understanding how the horn circuit works. The tower with the copper contact goes through the hole in the steering wheel and the contact touches the round metal disk in the horn button assembly. Unhook the battery until you get it all put together then hook the battery back up.

LockDoc

[landy]

You're right, I don't understand how the horn circuit works. I also didn't know the copper button or tower goes through the steering wheel, so I'll give your suggestion a try.

On a related note, I'm wondering if the steering wheel I now have is too thick. The truck came with an aftermarket small diameter wheel with all the horn components missing. I bought a used 2nd gen steering wheel to install. With the cancelling cam installed and then the steering wheel, the wheel is barely on the splined portion of the shaft. The wheel is way too wobbly because it's not adequately seated down far enough on the shaft. Without the cancelling cam installed, the wheel seems too close to the steel outer column, almost rubbing against the column.

Is there a difference in thickness between the 1st gen wheels and 2nd gen wheels? Were there different thicknesses of cancelling cams?

Thanks!

[LockDoc]

Originally Posted by landy

You're right, I don't understand how the horn circuit works. I also didn't know the copper button or tower goes through the steering wheel, so I'll give your suggestion a try.

On a related note, I'm wondering if the steering wheel I now have is too thick. The truck came with an aftermarket small diameter wheel with all the horn components missing. I bought a used 2nd gen steering wheel to install. With the cancelling cam installed and then the steering wheel, the wheel is barely on the splined portion of the shaft. The wheel is way too wobbly because it's not adequately seated down far enough on the shaft. Without the cancelling cam installed, the wheel seems too close to the steel outer column, almost rubbing against the column.

Is there a difference in thickness between the 1st gen wheels and 2nd gen wheels? Were there different thicknesses of cancelling cams?

Thanks!

I don't know about the wheels but I'm sure the cams are different between the old and new.

I would take that wheel off and get a stock one. At least until you get everything working correctly.

LockDoc

[landy]

So the copper button doesn't fit through any hole in the steering wheel that I have. I've looked at some pics of original style cancelling cams and they look like the same width.

So does anybody know if there's a difference in width between the 1st gen steering wheel and the 2nd gen steering wheel? See my below post.

Thanks!

[LockDoc]

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Like I said in the post above, get a stock wheel and put on it...

LockDoc

[landy]

Perhaps easier said than done. Used 1st gen wheels in decent shape are hard to come by. And the repros on LMC are lots of $s.

I'd really like to know if there's a difference in steering wheel width between the two. If there isn't, I have some other problems besides the horn.