Taillights & blinkers driving me nuts. Not sure what else to check

[ih8vols]

79 Silverado stepside

About a year ago I upgraded that lights to LED’s so they would be brighter. Everything worked fine.

If the truck sits for too long, there’s times the rear lights won’t work at all (blinkers, sidelights on rear, brake lights). The couple times I’ve fixed it by retightening the grounds from the tail lights to the bed. It fixes it.

Last weekend, I went to drive the truck and realized the taillights weren’t working. Backed it into the garage. Did my usual tightening of ground wires and they worked. I pulled the truck into the driveway and they stopped. The license plate lights still worked.

Tried my ground wire trick again. Nothing. Jiggled the rear harness and the license plate lights went out.

The previous owner had added trailer wires before the rear harness plug and it was a ball of crazy. I decided to cut that mess out and cleanly wired everything back up. Still zero lights.

I disconnected the grounds going to the side markers and put them to the bed with the tail lights. Nothing.

I added a ground strap from the side marker ground and tail light ground to the frame. Nothing.

All the fuses are fine.

I checked continuity with my multimeter on the intermediate harness and got a current.

Any more ideas on what I can check? I’ve spent hours on this thing today and gotten nowhere.

Appreciate it.

 

[rusted nuts]

79 Silverado stepside

About a year ago I upgraded that lights to LED’s so they would be brighter. Everything worked fine.

If the truck sits for too long, there’s times the rear lights won’t work at all (blinkers, sidelights on rear, brake lights). The couple times I’ve fixed it by retightening the grounds from the tail lights to the bed. It fixes it.

Last weekend, I went to drive the truck and realized the taillights weren’t working. Backed it into the garage. Did my usual tightening of ground wires and they worked. I pulled the truck into the driveway and they stopped. The license plate lights still worked.

Tried my ground wire trick again. Nothing. Jiggled the rear harness and the license plate lights went out.

The previous owner had added trailer wires before the rear harness plug and it was a ball of crazy. I decided to cut that mess out and cleanly wired everything back up. Still zero lights.

I disconnected the grounds going to the side markers and put them to the bed with the tail lights. Nothing.

I added a ground strap from the side marker ground and tail light ground to the frame. Nothing.

All the fuses are fine.

I checked continuity with my multimeter on the intermediate harness and got a current.

Any more ideas on what I can check? I’ve spent hours on this thing today and gotten nowhere.

Appreciate it.

Check Amps,, Just cause you have current don't mean you have enough Amps to light them up.

 

[fast 99]

Try removing the LED bulbs and install regular incandescent.

 

[Randy and Easton]

I’m with @fast 99 on this as a start. You’re checking all the right stuff for sure. Keep us posted please

Randy and E

 

[WP29P4A]

You handled the first step in trouble shooting an electrical problem, you established a pattern. Now verify the problem by taking a long piece of wire, attach it to the negative terminal on the battery. take the other end and touch it to your ground wires for the tail lights. If the lights start to work you have confirmed the problem. Remove the ground wire, clean all rust and paint from the ground location, use a fresh clean screw or bolt, use a star washer to bite into the metal for a better connection, replace the connector on the end of the ground wire. Use dialectric grease to keep the connection from rusting. If you strip the wire and the copper is black, the wire must be replaced.

Then check the ground at the front of the truck that ties the bed to the battery, the frame to battery. If you don't have a good ground from the battery to the body and frame, nothing you do at the back of the truck will matter.

 

[ih8vols]

I’m sure you guys can relate to this update….decided to pull the truck in the garage today since it was raining so I could troubleshoot. My wife happened to be in the garage as I was backing up. I back up and shut it off. She gets excited “You did it?!? You fixed it??! The lights are on and bright!”

I did nothing but start the truck and back it up this morning and everything worked.

Gonna work on it some today to see what I can find.

As of now, brake lights and back up lights work.

The tail lights nor rear side markers come on when I turn the headlights on right now.

 

[WP29P4A]

You are dealing with loose or corroded/oxidized connections, also don't forget the connection most people give a free pass too, the connection between the wire and the crimped on eyelet connector at the ground location. The moisture is helping the connection pass voltage until it dries up, then the problem will return.

 

[PrairieDrifter]

Also check that quick disconnect plug that's supposed to be just off the frame.

 

[fast 99]

You are dealing with loose or corroded/oxidized connections, also don't forget the connection most people give a free pass too, the connection between the wire and the crimped on eyelet connector at the ground location. The moisture is helping the connection pass voltage until it dries up, then the problem will return.

Exactly, I hate it when customer vehicles "fix" themselves. You know a dissatisfied customer will return.

 

[ih8vols]

Exactly, I hate it when customer vehicles "fix" themselves. You know a dissatisfied customer will return.

You are describing my wife. Lol. She couldn’t figure out why I was still aggravated and not happy everything was working.

 

[Zelph]

I have nothing to add than what has already been said. Just marking this thread to follow for the solution.

 

[Dixie Pride]

I am not an expert just restoring my 85K20 i bought new.Had a simular problem it was the turn signal swithch inside the steering wheel. If affects more lights than just the blinkers. Replaced it and everthing worked fine.Just a thought not sure if this has anything to do with your problem.

 

[ih8vols]

So, I ended up going back thru all my wiring. The issue was the ground between the bed and frame. I added a grounding strap between the two and everything is great.

I think if there was just enough weight in the correct spot on the bed, the two would touch and ground. Or if there was moisture it would complete the ground.

Appreciate all the help. Crazy how a $1 fix can send you into circles for hours.