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Air horn woes
- Thread starter tbar123
- Start date
- 1,450
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- Gray, GA
You could have continuity to both ends of the wire in the column and still be grounding inside the column too. Check continuity between one end of the wire and the column itself to rule this out.
I never thought of that! Test #3 for the day!
His mentioning that disconnecting wire 25 from the horn switch stops the horns from sounding is what leads me to believe the switch is providing GND when it shouldn't be.
74M35A2
Well-known member
- 4,145
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- Livonia, MI
I was in a mess like this with my fuel gauge. Big surprise. I swapped gauge, NG. Put original back. Swapped sender, still NG. I then connected the new gauge and new sender together on the bench and supplied 24v to it. It worked perfectly. I swapped both into the truck, and the system works perfectly. Both my original gauge and sender were bad. Trying to diagnose just one by swapping parts didn't solve it, and it was such a simple system. If this keeps driving you nuts, you may need to see if you can get it to work properly once removed from the truck and place the horn system on a bench with external power supply. That would at least tell you if the problem is with the horns and attached solenoid, or vehicle side wiring. Maybe you have a spider lodged in the solenoid, or the solenoid has a short to ground inside its case, or a solenoid spring or seal is not together correct and the air pressure is blowing it open. It should be a simple system, and a DVOM should be able to tell if the issue is mechanical or electrical.
- 1,450
- 118
- 63
- Location
- Gray, GA
#25 is the only wire in the column. The button connects it to Ground when pressed. If #25 grounds inside the column then the switch is bypassed and the horn will stay on indefinitely. He stated that he removed the wire to the button at the BOTTOM of the column which would take the button, and any short, out of the circuit simultaneously. If he disconnected the button at the top from wire #25 then I'd be inclined to agree with you since the circuit is being broken between the places in question. A diagram from the P2P is below.
This is the comment that leads me to believe it may not be a shorted wire inside the column. Unless the short was taken away at the same time wire 25 was removed from the horn switch. Thorough investgation of the wire 25 insulation may reveal whether or not a short is occuring.
Been there before. It's when more than one seemigly impossible sepetate problems occur that the head scratching really begins!
New results in.
I removed 25 from the solenoid-no horn
I removed the horn switch case-horn still blows
I tested for continuity between horn button wire,column case and all 4 switch mounting holes-none
I tested the ground wire inside the switch for continuity-none
I thought maybe the column was coming in contact with the fire wall so I pulled in back through the opening and rested the end on the rubber floor mat and horns still blew.
I checked for continuity between the horn button wire and all over the brush plate-none
I removed 25 from the solenoid-no horn
I removed the horn switch case-horn still blows
I tested for continuity between horn button wire,column case and all 4 switch mounting holes-none
I tested the ground wire inside the switch for continuity-none
I thought maybe the column was coming in contact with the fire wall so I pulled in back through the opening and rested the end on the rubber floor mat and horns still blew.
I checked for continuity between the horn button wire and all over the brush plate-none
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Check for continuity to ground with 25 disconnected from the horn solenoid, so put one lead on the wire(truck side, not the solenoid) and the other lead to ground.
Obviously, 25 is grounding somewhere to make the horn function.
Follow it to the column,it may be pinched somewhere or damaged somewhere.
Obviously, 25 is grounding somewhere to make the horn function.
Follow it to the column,it may be pinched somewhere or damaged somewhere.
Alright, I did the test that doghead suggested and something seemed weird with my ohm tester, So I put the 2 leads together and 1.8 So that was alright. So I took them apart for about 5 seconds reconnected them and it was 7. did it again and what do ya know 15 something. So I can't rely on this tester and have to get a new one and redo all of these tests. I just LOVE IT!!!!
Actually I don't think there is anything wrong with your tester. Touch the test leads together and see what kind of difference the readings are. If they are more accurate then the variation you see may be a clue that there is a conductor/wire touching GND somewhere. This is typical when the short is not making a good enough connection to get repeatable ohm reading however it is good enough to activate a circuit. I think you are finally onto something!
I don't think it's anything to be concerned about. You could try some light sandpaper on the test leads to clean off any oxidation buildup.
Ok, I did all the tests that were suggested and even made a seperate wire from the solenoid to the horn switch. The horn didn't blow at 60, but at 120 I pushed the horn button and it still didn't work. I redid the Doghead test and it said the wire was grounding somewhere. But by bypassing that shouldn't the horn work?
Yes it should work with a jumper to the solenoid. You may have more than just a shorted wire problem. The switch could be defective, or the ground on the other side of the switch is not connected well etc.
I got back at it today, and this is what I found.
1) I made a jumper cable from solenoid to horn switch,horn did not blow at 60 or above psi.
2) I reconnected the fusible link/diode and the plugged 25 back into horn switch,horn blew.
3) I detached 25 from the horn switch then jumped to steering wheel nut, worked as should.Did the same with jumper wire, worked fine.
4) I cut apart my old steering column and couldn't see anything that would/cause a failure in the steering column.
5) Accidentally dropped my phone and am now out hundreds of dollars! Pretty bad day,But life is still good.After all I woke up and I do have beer!
1) I made a jumper cable from solenoid to horn switch,horn did not blow at 60 or above psi.
2) I reconnected the fusible link/diode and the plugged 25 back into horn switch,horn blew.
3) I detached 25 from the horn switch then jumped to steering wheel nut, worked as should.Did the same with jumper wire, worked fine.
4) I cut apart my old steering column and couldn't see anything that would/cause a failure in the steering column.
5) Accidentally dropped my phone and am now out hundreds of dollars! Pretty bad day,But life is still good.After all I woke up and I do have beer!