1986 M1009 Rear Light Nightmare

[TrashyRacoonKing]

If this has been answered and someone can point me in the right direction I will gladly head that way, but I haven't been able to find the exact situation. I've been a LONG time lurker, but never needed to ask a question and I finally purchased a 1986 M1009 that sat since 2016 from my neighbor. I used to drive this exact truck at least once a week for my neighbor. He was wheelchair bound, and would never sell me the CUCV. He passed in February, and left me this glorious beast in his will. He never said anything about it, never told me it was to be mine, but now I have to get "Ranger" back on the road in his memory. First thing I did after I got it towed to the house was replace the batteries and she roared to life, ready to once again get on the road. I've almost got her state inspection (El Paso TX) worthy! I know a couple of bucks will help me get her passed BUT I have run into a huge issue. This will fail me OR get me pulled over. I've tried chasing wires and replacing a few parts. Was hoping this community can pinpoint the cause.

Symptom: When I put on the directional to turn right towards the Passenger Side, I will get the following 3 bulbs to light up. The actual direction light on the passenger side, the backup light on the passenger side, and the backup light on the driver side all blink together in sync.

What I have done:
1. I checked all bulbs, all 6 bulbs light up and work. I have switched them between both the driver-side and passenger-side rear lights to verify.
2. I replaced the 10amp stop and tail light fuse (which was actually blown) with a brand new 10amp fuse.
3. Replaced the Hazard flasher and Signal flasher fuses with brand-new fuses.
4. Checked to see if putting on the hazard lights makes a difference. It does not have, the same symptoms.
5. Checked to see if putting on the driving lights makes a difference. It does not have, the same symptoms.

I can send videos and photos if needed.

Any help, pointers, gremlin finders, anything would be appreciated.
-Trashy

 

[Black Ops]

I’d check your grounds.

 

[TrashyRacoonKing]

I’d check your grounds.

Trying, but at some point someone owned this truck and literally threw wires at it and turned it into a spaghetti mess. I have wires that dont go anywhere. Been trying to untangle the mess as I've been following wires. Ill probably get out there tomorrow and try chasing the wires.

 

[TrashyRacoonKing]

Small update. Following what Black Ops recommended. Checked initial grounds behind lights.

1. Loosed Driver side ground. All rear driver side lights blink in sync. Tightened it back to just driver side turn signal.
2. Loosed passenger side ground. Passenger turn and day light blink in sync.
3. Loosen both passenger and driver. Both tail lights dead.

Just trying to see which harness to follow at this point

 

[Barrman]

Basically, there are only 4 wires going to the back of the truck for service lights. There are the black out lights and the fuel sender wire as well.

Have you considered the former military vehicle registration or antique registration? No inspection required. If you wait until January. Regular tags won’t need inspection either.

 

[TrashyRacoonKing]

Basically, there are only 4 wires going to the back of the truck for service lights. There are the black out lights and the fuel sender wire as well.

Have you considered the former military vehicle registration or antique registration? No inspection required. If you wait until January. Regular tags won’t need inspection either.

I found were they are now running along the frame. I lost enough daylight and steam to finish today. Ill chase them down this weekend, I might even just bite the bullet and replace the stalk to make sure it isnt the multi-function switch. I have considered both but as the CUCV will become my daily driver I technically dont qualify for the former military vehicle registration. At the end of the day I have a turn signal that causes all my lights to flash. I still have to drive on and off base and we know MP's/Cops can either be cool, or be jerks. I would prefer to make myself the smallest size target for either.

 

[royalflush55]

It could be the bulb sockets have the broken ground tab. This is common.

 

[TrashyRacoonKing]

It could be the bulb sockets have the broken ground tab. This is common.

Okay I consider myself a car guy, but am by NO means a mechanic. When you say broken ground tab are we talking about the uneven star washer, the actual tab that something like the taillight housing would screw into that holds the bolt steady, or did you mean something else? Any help is greatly appreciated.

 

[TrashyRacoonKing]

Team,

Came home from work and decided to take a hose to the engine bay. Carefully made sure not to spray water onto the batteries, electrical connections, and alternator. Besides having a fairly clean engine bay now, no change in situation.

 

[Barrman]

Here is a video I did about the ground tab on the fron blinker socket and replacement:

 

[TrashyRacoonKing]

Barrman, I'll take a look at the video. Also found Warthogs sticky with ALL of the diodes and electrical connections. Trying to chase down this gremlin. Figured out the horn doesnt work as well. Found the thread on how to fix that.

 

[placek59]

My coworker had a similar situation on his front signals on his civilian k5 blazer. I think his is a '79 and a gas burner if that matters...

It was a bad turn signal socket.

 

[TrashyRacoonKing]

So today was a bright and sunny day here in El Paso. Decided to ditch work a bit early to come home and see what I can find out.

Checked the bulb sockets like many of you suggested. Great place to start.
1. Started with the passenger side, turn signal/backup are getting around 12v during "Blink" and drops to about 5v when off.
2. Moved to the Driver Side backup bulb was getting 12v during its blink. Okay, thats the right voltage at least.
3. Lets check the 2 rear grounds right behind the light housing again. All cleaned and tightened.
4. Checked the plug connectors that go from the wiring harness to the lights themselves. Dirty on the outside. Clean on the inside. Lets check and see the voltage... Yep... Driver side wiring harness plug pushing 12v during the "blink"... Hmmm.
5. Lets start chasing cables, found the cables run up the driver side frame. Was not able to find any further grounds.
6. Follow the cables into the engine compartment.... Yeah... I think I found the issue. For those thinking it was a fire that caused it, your wrong. Its grime. Dirt, oil, filth. Im going to purchase a decent brush and some WD40. I hope this is the cause... I'd really prefer not to have to buy a rear wiring harness.

Will update with results.

 

[nyoffroad]

I might have missed it but did you check BOTH tail light grounds at the body? Each light has a black wire going to the truck body, the need to be clean and tight, the truck bed needs to have a clean ground also, it should be grounded thru all the bolts to the frame but who knows?

 

[Barrman]

Unplug the ground from the front battery before you pull the pictured plugs apart. You will find it is actually 3 different plugs going into the back of the fuse panel. Engine, front lights and rear lights. The 3 plugs kind of snap apart and back together.

There will be a black goo inside the contact pin area. That was applied at the factory. A little fingernail file seems to work and cleaning the pins up.

 

[TrashyRacoonKing]

I might have missed it but did you check BOTH tail light grounds at the body? Each light has a black wire going to the truck body, the need to be clean and tight, the truck bed needs to have a clean ground also, it should be grounded thru all the bolts to the frame but who knows?

Roger. Found both grounds, cleaned, and reseated both grounds behind the tail lights. Chasing the wires I only found a total of 2 grounds. Both behind the tail lights. From the rear to the front into the engine bay I couldnt find any others.

 

[TrashyRacoonKing]

Unplug the ground from the front battery before you pull the pictured plugs apart. You will find it is actually 3 different plugs going into the back of the fuse panel. Engine, front lights and rear lights. The 3 plugs kind of snap apart and back together.

There will be a black goo inside the contact pin area. That was applied at the factory. A little fingernail file seems to work and cleaning the pins up.

Tracking. Thought they were pulls at first, not slides. Thankfully once I unbolted it I found its a slide, not a pull. Cleaned the ever living daylights out of it. Used a nail file like you suggested. Found 2 bent pins, reseated everything....

Still have the same symptoms. Wondering if it is the relay now. Glad I cleaned the block, lord knows it needed it. Will check the relay tomorrow. Hoping. Praying its the relay under the dash at this point

 

[WWRD99]

Tracking. Thought they were pulls at first, not slides. Thankfully once I unbolted it I found its a slide, not a pull. Cleaned the ever living daylights out of it. Used a nail file like you suggested. Found 2 bent pins, reseated everything....

Still have the same symptoms. Wondering if it is the relay now. Glad I cleaned the block, lord knows it needed it. Will check the relay tomorrow. Hoping. Praying its the relay under the dash at this point

Ok going back a few to line 1 you said you checked voltage when on and it was 12 volts but off it was 5 volts...you found your problem...you're missing the ground at the headlight for that side...it's backfeeding the system. When it's off you should have 0 volts.

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[TrashyRacoonKing]

Ok going back a few to line 1 you said you checked voltage when on and it was 12 volts but off it was 5 volts...you found your problem...you're missing the ground at the headlight for that side...it's backfeeding the system. When it's off you should have 0 volts.

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But that's just it. I can't figure out where it's getting the backfeed from. Aside from ripping the entire wiring harness out I'm at a loss here. I'm about to just self tap a new ground

 

[WWRD99]

But that's just it. I can't figure out where it's getting the backfeed from. Aside from ripping the entire wiring harness out I'm at a loss here. I'm about to just self tap a new ground

I just told ya!! Front turn signal...it's up top of the coolant res or just in front of the front battery...could be the bulb socket internal side ground too...take bulbs out and see if things change.

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