Hey folks, I am a serious newbie to this forum.

I was driving home today and all of a sudden, my horn went off and I smelled (and saw) smoke in the cab. I pulled over and quickly disconnected the horns ans smoke dissapated. Got home and still measured 12 volts on the horn contacts. I pulled the relay and fuse and then poked around under the dash. I expected to see wires with melted insulation but to my surprise, I did not see a thing. Everything else seems to work so I have 2 questions. 1. If the short did not blow the fuse, I still may have a hot to ground issue, correct? and 2. Does anyone know where I can get schematic for horn circut? Thanks in advance.

 

1. Your clock spring probably broke, & that's what nearly caught fire. Click this link for plenty of pics & diagrams.

2. The first is the simple version. Where it says "sliding contact" is where you have a clock spring.

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Steve83, Thanks for your help. I was wondering if possibly clockspring. Does anyone know if I can chk continuity to verify before getting into steering column? I also wonder why smoke instead of blowing fuse but I guess that is my Xmas present. Thanks again for your help.

 

The pics in that first link show how to get to the clock spring connector under the dash, & how to pull the airbag to get to the other end to check continuity thru the spring.

Of course, the factory circuits are protected by fuses. But when they start shorting together, there's no telling what could happen. The traces in the spring are very fine, so with enough current, they'll burn the plastic off, like a rear window defroster running at 100V.

 

Thanks, I have a dead short on relay connector to steering wheel so I guess it is time to disassemble the column.

 

I checked the clock spring for continuity and it seemed OK. I thought moving it around might have opened the short so I replaced anyway (Thanks for guidance). Unfortunately, That did not fix my problem (anyone need a good clock spring?) Anyway, there is still a short on one of the relay connectors. It is the spade connector closest to fender, My diagrams I have do not have enough detail to let me know if there are other components in this circuit and I loose track of the wire under the dash going to a large connector. This connector has numbered pins but sits behind the large aluminum structure. Does anyone have a detailed diagram of a 95 horn circuit and can you share the connector numbers? I am hesitant to pull the fuse box apart that sits in the engine compartment. Any help would be appreciated.

 

If the smoke didn't come from the clock spring, then the wire that it DID come from is probably the one that's shorted. Try to follow the smoke residue & melted plastic to the source of the smoke & find the root cause & location.

If you can tell me the wire color & a physical location of the wire you're trying to follow (like terminal 84a of the horn relay, or something like that), I can look it up. If you want your own CD that shows everything (& more), e-mail me.

 

Thanks Steve83 will email you. In the mean time, Does anyone know physically where the alarm circuit and the horn circuit hook together? My Haynes manual is useless for wiring.

 

Remember to post that info you e-mailed me so (everyone else &) I can see it all here.

Haynes hasn't revised 36058 since '92, so it doesn't show airbags, RKE, or alarm wiring. They were introduced later. Otherwise, it's the best source for diagrams, other than the factory disks.

I just thought of another POSSIBLE source for the smoke - maybe the airbag was triggered by the clock spring going bad, but it didn't detonate properly. Just an idea. Pull the 4 10mm nuts from the front (away from you) of the steering wheel, & lift the airbag off so you can inspect the back. If it blew, there should be obvious signs of heat & smoke. It's perfectly safe to handle or disconnect the airbag, as long as the key is OFF. If the key is in RUN, you won't blow the bag, but you could ruin the diagnostic module.

 

Here is what I emailed. I did check the airbag and everything looks good.

Steve, first, thanks for your help. I have not seen any melted wires or
>> the source of the smoke. I also am colorblind (really) so it is difficult
>> for me to distinguish the wire color. It appears to be yellow with blue
>> tracer on the clockspring side converting to dark blue at the fuse box
>> side of the connector. I loose it when it goes into the bundle and can
>> barely see the bulkhead connector except a few numbers. I assume (not
>> good
>> thing) the issue is under the dash because smoke was inside the cab. I
>> think the alarm circuit (factory) cuts in somewhere but I con not see
>> where. I have yet to disassemble the bulkhead connector as I am skeptical
>> from previous experience on aged cars. I would appreciate info on
>> acquiring the CD. You have been a great hep and it is most appreciated

 

Did some more poking around this am. It appears the blue wire from the clockspring to the bulkhead connector goes to position 56 on the bulk head. I disconnected (just loosened) the bulk head connector (10mm bolt on firewall side ) an short left the horn relay. Put connector back tight and short was back. To correct earlier post, it is not a dead short. it appears to be around 5k ohms. (I am not an ee but I think this correct). This kind of validates the problem is inside the cab, so I am back to thinking there is a connection inside the cab I am not aware of (like theft alarm). Any help is appreciated, I miss my truck.

 

5K Ohm is the opposite of a "short". Short Circuit means that there's not enough resistance, so too much current flows thru. At 12V, 5K Ohm doesn't pull a quarter of a 100th of an Amp. Exactly where & how are you measuring this 5K? And what symptom made you think there was a problem with it? Is the horn still stuck on? Even with the relay removed?

Your quickest solution is to find where the smoke came from & follow it. Did it come out of the steering wheel? Or from under the dash? Or out of the ventilation? Or from the glove box? Around the instrument cluster?

 

OK, I am not real good with ohm meter but will try and explain. There is 12v at the horn connector unless I unplug the relay. The spade connector on the horn relay socket closest to the fender ( no diagram so I can't ID connector number) Is where I measure. I put lead red lead from ohm meter on this connector and black lead to frame ground. With meter on rx1k, I get a reading of 5 (which is halfway up the meter scale). If I mash the horn button, it moves all the way to the right (my definition of short). If I plug the relay in with battery hooked up, I can hear it pick. I have tried other relays as well in this spot. I then go to the connector in the cab and isolated it to the yellow/ blue wire out of clock spring ( replaced the clock spring. This shows same indication as the relay measurements. If I disconnect the clock spring,and measure on firewall side, I still see that resistance )half way up the scale but clock spring and rest of steering column are out of the circuit. To isolate whether this cause of this indication is inside or outside cab, I disconnected the bulk head connector and the "short" went away when measured at the relay. I assume the problem is between the bulkhead connector and the clock spring connector at the mid point of the steering column. I have looked and looked for burnt or disfigured wires under the dash because there was a puff of smoke at the same time my horns went off without doing anything. I am not sure where under the dash It came from but everything else seems to work.

 

You can't measure resistance accurately on a "hot" circuit, and right on an ohmmeter is typically HIGHER resistance. A "short" is low (or no) resistance. High or infinite resistance is called an "open" circuit. But again, you can't measure it accurately if the circuit being tested has power on it.

For a powered circuit, you must measure voltage.

The "CLICK" as you pull it out of the socket indicates a short in one of its trigger wires, but the fact that the needle moved when you pressed the button suggests there ISN'T a short in that circuit.

Again, referring to this diagram, you can see that there is no Y/Bu wire associated with the horn at the clock spring, so IDK what you were testing there.



The only thing that MIGHT be on your truck but not shown there is a tap from the DB wire going to the RKE/Alarm module, which is mounted above the gas pedal behind the dash pocket. Look up there & unplug it. Try to notice if there's any sign of smoke/heat around it.



That pic shows it with the knee bolster removed, looking straight forward. It has three connectors, so look for the one with a DB wire in one corner.

 

Thanks for your persistence. I will stay away from the ohm meter since I am uncomfortable with it. Here is a summary of what I did;
Hook everything up and put volt meter on horn wire at horn. To my surprise, everything looked good (no voltage). I pressed the horn button and my 12v came on and stayed on. I disconnected alarm connector, still on. I disconnect clock spring and still on. I pull relay and voltage goes away. I plug relay back in and it does not energize until I hit buttons. It appears that what I believe is a short to ground is enough to hold the relay, but not pick it. I did not see any melted wires around the alarm module but it is raining and I will look better later. Again, thanks for your Patience and education.