M1009 Horn Problems with hack job wiring

[Russm]

New to me M1009. According to previous owner it used to be a cop car. Previous owner removed most of the extra cop wiring.
Horn does not work. Horn was spliced to a 24v source from the fuse box. This 24v wire was probably attached to some kind of relay (had loose ends under the dash)... not really sure what the cops were doing with it.

Removed cop 24v splice. Attached hot wire (red) straight from battery to cut horn wire in first pic. Horn did not sound. Checked with a multimeter: Red probe to horn 12v input and black probe to horn ground screw = reads 12v. All connections up to the horn from the hot splice read 12v.

You're going to tell me its a bad horn... but wait...

Transplanted my horn to my brother's M1008... it works in his truck. But not in mine.

Closeups of the hot wire splice and of the horn connections behind the grille.



Give me some ideas

 

[dependable]

This is one of many useful posts you should check out in the CUCV sticky. Note picture and location of horn relay. http://www.steelsoldiers.com/showthread.php?50551-CUCV-Switches-Diodes-Relays

 

[Russm]

Was debating whether or not to mention the relay. I guess I should have.
Swapped relay from my brother's working horn to mine just to be sure. Orange wire shows 12v when service lights are switched on. My relay works in his truck. I still have no honk with his relay. I dont think its a relay problem.

 

[dependable]

If wiring to relay and relay is working, you should be able to here relay click when you push the horn button. If is good to there, remove the radio suppression capacitor from circuit (in your second picture, it just un plugs) that is hooked up before horn, clean contacts and ground. If still not working, check wire continuity from horn relay to horn, it may have been cut during prior modification.

 

[Gripy]

At the relay; will jumping the orange wire with green wire make the horn go off?

 

[Warthog]

If 24v was supplied to the horn it is toast. Remove all the crap wiring and put it back like factory. Also remove the capacitor at the horn.

 

[Russm]

Relay does not click when horn button is pushed. I think the cops may have messed with the ground too.

 

[dependable]

Here is a recent post with a good place to start. http://www.steelsoldiers.com/showthread.php?126973-horn-contact-replacement

 

[MarcusOReallyus]

1. There should not be 24v at the fuse box. The truck is standard 12v except for the starter and glow plug system (and most of the GP system is 12v).
2. Check your grounds.
3. Read the stickies already recommended.

 

[Russm]

Thanks for the replies.

Found one more cut wire, not sure where its supposed to go. This is the underside of the steering column, with the plastic semicircle "sleeve" and the metal plate the sleeve screws to removed.
I think the cut wire is the ground for the horn button.

The TMs aren't detailed enough, unless I missed something.
If someone could post or say where this cut wire is supposed to go, i think this may be my last horn issue *crosses fingers*

The pliers are pointing to the cut wire, with the closest clip connected and disconnected.

 

[Warthog]

Is that wire black? Hard to tell from the picture

 

[Warthog]

The horn circuit is very basic.

Here is the circuit from the wiring diagrams in the TM 9-2320-289-34 tech manual. They are in the appendix. Please read the first few pages of Section 2 Troubleshooting to learn how to read the diagrams.



From diagram E-20 the horn circuit is as follows.

1 - Power is from the horn fuse. It travels the orange wire labeled 1 ORG-24C to the horn relay
2 - The orange wire supplies power to the relay coil and the horn when the relay is energized
3 - The black wire is the ground for the horn relay relay. The horn button supplies the final grounding. The black wire travels from the horn relay to the flat harness connector at the base of the column. It travels up the column to the horn contact ring. The round contact ring uses the silver contact that attaches to the horn button. When you push down on the horn button, the ground circuit closes and allows the horn relay circuit to energize.
4 - When the horn relay is energized power travels down the green wire to the wiring harness connector on the firewall. passes through the firewall and on to the horn itself.

A couple of known issues with the CUCV horn circuit are the A) diode on the back of the horn relay connector. They can fail and allow the horn to operate at all times B) the noise suppressor at the horn. They fail two ways. They will not let the horn operate or they will fail and draw a lot of current. The horn doesn't work, but the headlight fuse keeps over heating and melting the fuse. But wait what does the headlight fuse have to do with it? Have you read the headlight circuit sticky? If so you will know that the headlight fuse controls many other fuses and circuits. The horn circuit being one of them.

 

[Warthog]

Like I said before. remove the capacitor and see what happens



One of the simplest test you can do is to remove the horn from the truck and use a couple of wire leads and a battery to test it.

 

[Russm]

Yes the cut wire is black. It comes out of the bundle that attaches to that plug, but there isn't a forth prong on that plug so it isn't obvious to me where it should go.

Capacitor is gone. Took it out. Did not fix the problem. I will cut out the diode too when I get a chance.
I can try jumping the horn straight from the battery with two wires. The front battery should give me 12v if I jump straight to it iirc.

 

[MarcusOReallyus]

Yep. Do that first. If the horn is toast, replacing it is the next step. Good news is, they're cheap.

Next, when you are measuring voltage, are you using a meter? OR a test light? Meters are great, and meters are necessary, but meters sometimes lie. If you have a high resistance (like a corroded connection) upstream of where you are measuring, you can meaure the correct voltage on an unloaded circuit, but as soon as there's a load, your voltage drops, sometimes to near zero.

If you've been measuring with a meter, try a test light.

 

[eme411]

just for your info , when a PD installs siren control box, Federal or other makes the horn button in many cases is used for running the electronic air horn , do not start to cut out any factory items from the wiring system, I've had many ex police vehicles and the first place I check is under the dash and I've ALWAYS found little surprises , many of them hot leads that have not been secured, the cut wire you found on the steering column I think should be # 1 go to spot, then try to find the other end, hope this helps

 

[ODFever]

Warthog - Thanks for posting the horn circuit summary, and the common issues with the horn.

 

[Russm]

Thank you all for the help. Finally got it working.

The green wire between the horn and the relay was cut.
The ground wire between the steering wheel button and relay was cut. (Was a real chore to find this amid the wire diarrhea under the dash)
The horn was half burned out, I finished the job by hooking it to 24v by accident.
Removed the capacitor before the horn.
Cut out the dead diode at the relay.
The horn button plunger contact in the steering wheel was too short and facing the wrong way.
And the A/C output at the fuse box reads 24v, although this is unrelated to the horn, its good to note since the whole fuse box should be 12v

The diode probably went out when the police dept had it and I think they just stated cutting until the horn stopped beeping.

 

[Warthog]

Thanks for the update. Glad you figured it out

 

[swiss]

The horn circuit is very basic.

Here is the circuit from the wiring diagrams in the TM 9-2320-289-34 tech manual. They are in the appendix. Please read the first few pages of Section 2 Troubleshooting to learn how to read the diagrams.

View attachment 505582

From diagram E-20 the horn circuit is as follows.

1 - Power is from the horn fuse. It travels the orange wire labeled 1 ORG-24C to the horn relay
2 - The orange wire supplies power to the relay coil and the horn when the relay is energized
3 - The black wire is the ground for the horn relay relay. The horn button supplies the final grounding. The black wire travels from the horn relay to the flat harness connector at the base of the column. It travels up the column to the horn contact ring. The round contact ring uses the silver contact that attaches to the horn button. When you push down on the horn button, the ground circuit closes and allows the horn relay circuit to energize.
4 - When the horn relay is energized power travels down the green wire to the wiring harness connector on the firewall. passes through the firewall and on to the horn itself.

A couple of known issues with the CUCV horn circuit are the A) diode on the back of the horn relay connector. They can fail and allow the horn to operate at all times B) the noise suppressor at the horn. They fail two ways. They will not let the horn operate or they will fail and draw a lot of current. The horn doesn't work, but the headlight fuse keeps over heating and melting the fuse. But wait what does the headlight fuse have to do with it? Have you read the headlight circuit sticky? If so you will know that the headlight fuse controls many other fuses and circuits. The horn circuit being one of them.

Warthog is the BEST!!!!!!!!!!!