Headlights, Tail lights, and horn issues.

[Bama93]

Hey everyone, I’m brand new to the cucv world. I just purchased a 1986 m1008 two days ago and fortunately I ran across this page and it has been very helpful so far. But I think I have been over the forums where people are having similar problems to be about 5 times so far and I haven’t gotten my problems fixed yet. So any input will be greatly appreciated!
Now to the issues. When I bought this truck I was informed that the headlights didn’t work and no one could figure out why (seems to be pretty common after all of my research) so I found a thread on here about the BO switches and how they work. Unfortunately mine had already been removed. I do still have the connectors that the toggle switches would go to so I mad the two jumpers to get the service side working. Immediately I found that my horn, tail lights , parking lights, and blinker lights on the dash came on and stayed on. The headlight switch will turn the headlights on and off but nothing else.
I feel like this post is very long already so I’ll stop here. Please, if I haven’t given enough info, let me know and I will do my best to give more. Thanks!

 

[cucvrus]

Sounds like you need some used replacement switches. I can help if you would like. Trading is great fun.

 

[Bama93]

Sounds like you need some used replacement switches. I can help if you would like. Trading is great fun.

I might just take you up on that if I can’t find any close to home.

 

[v12venator]

First and foremost, welcome friend. Congrats on your new CUCV and I hope we can help solve your issues with the service lighting on the truck.

Now onto the fun stuff: workin on the truck. I would start by removing the horn fuse from the fuse panel so you can get to work rummaging through the wiring in peace. Next you're going to want to take a poke at your service lighting fuse with a volt meter and check to make sure you're not getting 24v power, and instead getting 12v power like a normal vehicle would be. After that's been established, you can start tracing wires throughout the harness to make sure you're hitting every component in the sequences of wires to see if that is the problem.

A good number of helpful links in the stickied thread can point you in the right direction for hunting down common electrical issues in the truck, but the best resource by far is going to be the appendices of the -20 manual for these trucks also available here on the site. Those TMs are very helpful booklets for operation, maintenance and repair of your truck. The appendices in the back of the -20 shows every single circuit for your truck to include starting, charging and the service light wiring diagrams. These are available in PDF format in the CUCV TMs section on the main page. If you have any more specific questions, we're always here to help as well.

 

[Bama93]

First and foremost, welcome friend. Congrats on your new CUCV and I hope we can help solve your issues with the service lighting on the truck.

Now onto the fun stuff: workin on the truck. I would start by removing the horn fuse from the fuse panel so you can get to work rummaging through the wiring in peace. Next you're going to want to take a poke at your service lighting fuse with a volt meter and check to make sure you're not getting 24v power, and instead getting 12v power like a normal vehicle would be. After that's been established, you can start tracing wires throughout the harness to make sure you're hitting every component in the sequences of wires to see if that is the problem.

A good number of helpful links in the stickied thread can point you in the right direction for hunting down common electrical issues in the truck, but the best resource by far is going to be the appendices of the -20 manual for these trucks also available here on the site. Those TMs are very helpful booklets for operation, maintenance and repair of your truck. The appendices in the back of the -20 shows every single circuit for your truck to include starting, charging and the service light wiring diagrams. These are available in PDF format in the CUCV TMs section on the main page. If you have any more specific questions, we're always here to help as well.

Thank you for the help and advice! I haven’t had a chance to tinker with it the last couple of days but maybe I can get back to it sometime next week. I’ll update when I can.

 

[MarcusOReallyus]

Welcome!

A few pointers:

1. It's not an 86, It's an 84. I don't care what the DMV thinks, when you are buying parts, it's an 84. The Army didn't want to deal with varying models from year to year, so they required all CUCVs to be built to 84 specs.
2. Rick (CUCVRus) is a great guy, and knows his stuff.
3. He's right - the easiest way to fix this problem is to return it to stock. (Rick is now cheering.) Once you have it fixed, then you can consider doing some modifications if you want. (Rick is now booing.) If it's stock, we can help you. If it's modified by the PO, it's all blind guesswork.
4. Here's your new mantra - "If its electrical, clean it. If it's rubber, replace it." Especially clean your grounds! ALL of them!

 

[Bama93]

Welcome!

A few pointers:

1. It's not an 86, It's an 84. I don't care what the DMV thinks, when you are buying parts, it's an 84. The Army didn't want to deal with varying models from year to year, so they required all CUCVs to be built to 84 specs.
2. Rick (CUCVRus) is a great guy, and knows his stuff.
3. He's right - the easiest way to fix this problem is to return it to stock. (Rick is now cheering.) Once you have it fixed, then you can consider doing some modifications if you want. (Rick is now booing.) If it's stock, we can help you. If it's modified by the PO, it's all blind guesswork.
4. Here's your new mantra - "If its electrical, clean it. If it's rubber, replace it." Especially clean your grounds! ALL of them!

I kind of figured that 84,86 thing out with these threads but thank you for confirming it for me! I don’t think I have major wiring issues. Here is what I do know to this point. With the “bypass wires” on the plugs where the switches go and the headlight switch in the lights are on. When I take the headlight switch out the go off. If my memory serves me correctly I should have power on the orange black wire from the plugs (which I do) but when I tested the other with just a cheap test light I also had power on an orange? wire. I’m not sure if I should have it there all time or not.

 

[cucvrus]

I was just figuring a plug and play situation. Plug the original switches back on the plugs and shazam. That was all I was saying. I would think there are going to be a lot of combinations in the 2 plugs to get everything working correctly. But continue and Good Luck. Be Safe.

 

[MarcusOReallyus]

I agree with Sir Rick. Make it stock, then troubleshoot. Much easier.

 

[cucvrus]

I mean a couple of expired Alabama license plates sent my way are redeemable for the Black Out switches. That goes for any other takers. I like trading. Be Safe.

 

[MarcusOReallyus]

Rick, one of these days I need to drive up there and see your license plate collection.

 

[HeisenBob]

I mean a couple of expired Alabama license plates sent my way are redeemable for the Black Out switches. That goes for any other takers. I like trading. Be Safe.

I might take you up on that if I can’t get mine working. Except I don’t have Alabama. A few from Texas though.

 

[cucvrus]

Texas is just a good. Just making an offer. I have so much stuff I will probably never need. Take Care and Be Safe. I do like trading. Money is everywhere. Trade is better in some situations. I like material possessions. So I trade items for items. Be Safe.

 

[HeisenBob]

Texas is just a good. Just making an offer. I have so much stuff I will probably never need. Take Care and Be Safe. I do like trading. Money is everywhere. Trade is better in some situations. I like material possessions. So I trade items for items. Be Safe.

That’s awesome. Thank you!

 

[Bama93]

Ok so I have found a little time to tinker some more and so far I have fixed my brake lights. (Fire department I got the truck from cut the white wire and straight wired to lights from brake light switch) I reconnected the cut wire and since I have my jumper on the BO switch the brake lights now work. I also had a problem with my courtesy lights staying on. I fixed that by tightening the ground above the passenger side headlight. They are now off and on when they’re supposed to be. Now here’s the troubles I still have : horn still not shutting off. I have cut the suppressor out already, no help. My tail lights won’t work, reverse lights won’t work, and my blinkers and hazards don’t work. I will be getting under the truck and checking grounds as soon as I have more time.
Just wanted to update y’all on the little progress that I have made so far and again I am open to suggestions. Thanks!

 

[v12venator]

I have cut the suppressor out already, no help. My tail lights won’t work, reverse lights won’t work, and my blinkers and hazards don’t work.

When you say the supressor, do you mean the ribbon cable on the bus bars in the engine compartment or the small cylinder on the back of the horn relay? Cause that is a good culprit to keeping the horn on when those diodes fail and allow power to pass through full time. If you've already removed that diode from the back of the plug, you will want to start ripping into the steering column next to see if your horn button is maintaining contact and powering the horn. The diodes on the back of the fuse box behind the flashers for your turn signal and hazard plugs may also be the reasoning for your inoperable turn signals/hazards, but then again it could just be your lack of the service light switch in the truck at the moment. These trucks' wiring layouts weren't exactly the greatest but there was some logic behind how they built them.

 

[HeisenBob]

Welp....add me to the list of folks with wiring issues. I think i figured out the black out switches. The right one in the UP position should allow all the lights to work. With it in the UP position, I get running lights, left turn signal, back up lights, and that's it. No brake lights, no head lights, the right turn signal might work but when I push up on the turn signal handle, it doesn't click and stay up. The hazard light lever broke when I tried to engage it....it broke completely out of the steering column. The voltage gauge is missing from the instrument cluster. Also, the WAIT light used to stay on after starting and it was hard to start. I changed all the fuses to new under the dash and the WAIT light goes off almost immediately and the truck fired right off. My list of gremlins is starting to grow....

 

[Bama93]

When you say the supressor, do you mean the ribbon cable on the bus bars in the engine compartment or the small cylinder on the back of the horn relay? Cause that is a good culprit to keeping the horn on when those diodes fail and allow power to pass through full time. If you've already removed that diode from the back of the plug, you will want to start ripping into the steering column next to see if your horn button is maintaining contact and powering the horn. The diodes on the back of the fuse box behind the flashers for your turn signal and hazard plugs may also be the reasoning for your inoperable turn signals/hazards, but then again it could just be your lack of the service light switch in the truck at the moment. These trucks' wiring layouts weren't exactly the greatest but there was some logic behind how they built them.

Well I might have cut the wrong thing. What I cut is right beside the horn itself.
Also wanted to update that I now have my tail lights fixed!

 

[v12venator]

Trying to picture what you're talking about in my head. Are you talking about the power connection on the drivers side of the actual horn behind the grill? Cutting that would have stopped all power going to the horn if that is what you cut. You might have otherwise cut the connection to your front drivers side blackout light on the bumper.

 

[Bama93]

Trying to picture what you're talking about in my head. Are you talking about the power connection on the drivers side of the actual horn behind the grill? Cutting that would have stopped all power going to the horn if that is what you cut. You might have otherwise cut the connection to your front drivers side blackout light on the bumper.

Trying to picture what you're talking about in my head. Are you talking about the power connection on the drivers side of the actual horn behind the grill? Cutting that would have stopped all power going to the horn if that is what you cut. You might have otherwise cut the connection to your front drivers side blackout light on the bumper.