air horn problem

[BLCampbell]

sorry in advance if i am repeating a question already asked. i have look through several threads and posts and cant find what i need. i have a 70 m35 and my air horn wont work. sometimes when i push the button it works great other times it wont work at all. i was wondering if anyone had a diagram to show me what wires to check or what parts may be out. i have an inspection coming up and need a quick answer. thank you anyone with any input and again i apologize if i am repeating any of this....i know how frustrating it is to see the same post twelve times.

 

[Flyingvan911]

It could be several things. The wire in the steering column, the connector at the end of that wire by the radiator, the solenoid on the horn. I am working on this with my own '70 deuce. There are wiring diagrams on here but not specifically for the horn circuit. There are also a few threads on this very horn issue.

 

[rlwm211]

The wiring diagrams are in
TM 9-2320-209-20-2-2

The technical manuals are located on this site as well as www.JATONKAM35s.com I would download a complete set and have them available for reference when you encounter a problem such as this.

As to your problem, one possibility is that you have the older horn button and switch in your column and that could be the problem. The older design was superceded by an upgrade kit and this was a result of problems that the older design presented.

Another possibility is that there is a bad ground which is intermittently losing contact with the chassis.

The horn has an electrically operated solenoid whcih you can check by disconnecting the wires to the horn, and with a jumper wire to ground in one terminal and connecting the other terminal to the positive post of the battery.

Caution is always advised when you are using jumper wires and connecting to the battery.

I would suggest that you take some time to familiarize yourself with the technical manuals. There are troubleshooting instructions within them.

I hope this is helpful.

RL

 

[Rambling Wreck]

Sounds like you probably have a bad ground. That, or you have a loose connection somewhere. Put a multimeter on it and you should be able to diagnose where the problem is.

 

[rosco]

Not covered so far is the fact that those horns can get dirt and crud in them (not to mention a heavy coat of paint, even inside), and or, when they don't work, somebody could have taken them apart, get them out of adjustment, and then they might sound puky, like a blat, not sound at all/or all of the above, just sometimes. So clean the whole thing, check the grounds. Maybe disconnect the air line between the solnoid and the horn, and blow in it with the shop hose. You might find that it works, then the problem is electrical. Maybe too, carefully take apart the horn button, and see how it works. Some simple ones, just contact a metal buttom with a hot wire, to make a complete ground. You can, if its out of adjustment, re-adjust it, but check it with a shop hose, or on the bench 1st... otherwise, if it needs adjustment, you can spend a good long day, fussing wth it, and be nearly deaf, by then.

 

[steelandcanvas]

Just to clear things up a little, folks are telling you to check your grounds. While this is good information, the horn solenoid has a constant (+) 24 volts to it, the circuit is completed by grounding (-) the solenoid via the horn button. The circuit is not like a light circuit where you switch the (+) and the light is already has it's ground (-). There are a few threads diagnosing the air horn problems, some of which I have previously offered troubleshooting tips on. PM me if you continue to have problems or get lost. Good luck!

 

[Cycletek]

This was one of the few "problems" my 5 Ton had, when I got it. I pulled the horn button off and found a light coating of rust inside. I jumped the wire to a known good ground and my horn sounded off. A little cleaning with some contact cleaner and some emery cloth and i had a nice contact surface to complete my grounding circuit as SteelandCanvas pointed out.......

 

[RedbeardTheZombieHunter]

I had the same issue so I pulled the horn button apart and found the brass contact areas were tarnished with enough green fuzz to prevent un-resisted contact. I took the button assembly apart and scrubbed the contact areas, then gave them a light coat of engine oil (finger collected off the dipstick) to preserve the fresh brass surface as airborn pollutants can cause brass to tarnish without acting as an insulator. No problems with the horn since and if I'm not mistaken, the button doesn't require as much pressure to sound the horns as it did before the horn button cleanout.

 

[misterbill64]

This is a little long winded but should let you find the problem in about 10 minuets

(1) With the air tanks fully charged and the master switch on, disconnect the wire where it comes out of the steering box, take the end that goes along the frame and ground it out on the frame if the horn blows the problem is in the column go to (2) , if not go to the horn , disconnect both wires and with a test light or a volt meter check both wires for voltage, if no voltage go to (3). If 24v plug the one with power back in, take a spare wire and attach to good ground , place other end on remaining terminal on horn if it blows the problem is a broke wire between horn and steering column, repair or replace as necessary. If it doesn’t blow the horn is bad, repair as necessary.
(2) Take a long jumper wire and connect it to the wire coming out of the bottom of the column, run it into the cab. Take the horn button lose and with a ohm meter check for continuity between the wire coming out the top of the column and your jumper wire. No continuity replace the wire in the column, continuity repair or replace the horn button
(3) check the circuit breaker on the firewall for voltage on both sides, if voltage on both sides trace the wiring from there to the horn to find the break, if no voltage trace the wiring from there back to the power supply to find the break

 

[steelandcanvas]

(1) With the air tanks fully charged and the master switch on...

The horn circuit is hot all the time, no need to turn the accessory (master) switch on to troubleshoot.

 

[SCSG-G4]

Another thing to consider, esp. if you have the large rubber type horn button that covers the whole center of the steering wheel. Pull the rubber cover off and see if the hard plastic piece underneath has clearance all around, and will easily go up and down. If not, you may want to trim off part of the inside of the steering wheel. Mine was warped and would stick down and not return (think stuck horn). A box cutter blade around the parts where it was tight fixed things up.

 

[pad_cdr]

Thanks for posting this question and risking the pummeling by those pointing out someone may have asked a similar question back in 1957. My horn has not worked since I got the truck. After reading the helpful answers, I took my horn button off to see if it had rust, corrosion, etc.

Nope, it turns out it was not plugged in to the lead wire inside the steering column. Shorting it out with needle nose pliers (not intentionally) showed that it tripped the solenoid, so I plugged it in, put it back together and nothing.

Figured out that the back of the button was not touching metal, so it could not complete a circuit.

Pulled up the manual, and looked at the horn button pictures. Whoops, I had a new type horn button not covered in the manual. That didn't help.

Did some searches in the Deuce section, and found a picture of the parts associated with my type of horn button.

Turns out there was supposed to be a spring between the back of the horn button and the steering wheel nut. Off to the hardware store and $1 later, had a spring that I could cut to length and a washer to help it make contact with the steering wheel nut (the springs they had were too small in diameter to rest directly on the nut). May still need to trim another coil off the spring, it pushes a bit too hard on the button assembly, but I'll leave it for now. Much easier to trim more off than to add it back on.

Horn works fine now, and I no longer need to disappoint all the little kids pumping their arms up and down when I drive by.

 

[Amer-team]

This is worth refreshing. Thank you for the tips in this thread. A friend came by today with his 923A1 and no horn. Ended up taking the horn button off, cleaning a lot of corrosion, and viola, the horn is working away again,. Cleaned the nut, spring, and push button. Horn works like a champ again.

 

[TB58]

really embarrassed to jump on this thread, but I can't get my horn button apart. I looked in the TM and it pretty much just says to remove it. I tried pushing it all the way in and turning it both ways, Tried pushing the brass piece down in the center hole and turning it. Do I just need to use my man hands and make it turn? I have a short some where in the steering column which gets kinda embarrassing when the horn goes off every time you pull into a parking lot.

 

[LiveFreeOrDieTryn2B]

Yes it has an isolated ground for the button and a constant hot I have to replace my hot wire no power .I eliminated the button off the steering wheel and put a button where my ether button once was.When I purchased the truck the column wire had a short so I just got rid of it all together.

 

[Amer-team]

TB58, what sort of truck do you have? M54 or 800 series. They have a twist the horn button type and it is a bugger if it hasn't been off for awhile. the M923 is easy with 3 screws holding it on. If you have the twist type, be patient or you will break a leg off.