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Discussion Starter #1
problem with factory trailer wiring . left output for turn signal is like 1.5 volts and that from the connector for the 7 pin plug. All lights are working fine on vehicle ..
 

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Check and make sure you absolutely have a good ground before doing anything else. Even simply run a 20/30 foot jumper from the vehicle to the lights your checking and connect it to a grounding bolt.

I was suprised to learn that my axle is not grounded to the rest of the frame on my boat trailer. I made that 15 foot jumper cable permanent with a couple self tapping screws. Which got covered with dielectric grease.

Bad grounds on trailers makes the lighting do weird things that make it look like it's somewhat working correctly when it's not. Your situation sounds exactly like what I had with my boat trailer.

Al
 
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Discussion Starter #3
problem with that is the ground on the factory wiring is fine as i can get accurate measurements from right side signal/ brake lights and parking lights are all fine its the left signal as far as i can tell .It sall on the vehicle side where the issue is but thanks
 

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You've got corrosion somewhere, follow the harness back to the split under the bed, inspect the connector
 
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Ahhhh I thought it was trailer side.... well the back of the truck is exposed to the elements but it is all simple plug n play connections so they can easily be taken apart, cleaned and inspected.

Clean them up with electrical contact cleaner and a small drill bit or file. Dont ever crame these or any connection with dielectric grease as it prevents an electrical connection, instead it can be used to lubricate the rubber grommets on the plug which will keep water out.

Al
 
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Discussion Starter #6
thanks.. but think i need a manual to find the wiring path as it has nothing to do with the plug .. there is a voltage drop in the wire itself ahead of the puck /plug.
 

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What are you working on?

The rear tail lights are wired into the same wiring via these plugs.... one runs to the right n to the left... they are pulled apart and the trailer connection harness is added here. so if your brake lights, turn signals and running lights work, then we can assume and verify that the main wiring harness running to the front is indeed intact and working. It's all plug and play so you should be able to pull it apart very easily to check things. it could be the trailer harness section but it's probably corrosion.

But just to be sure what vehicle are you working on?

Al
 

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As Al said, it sure as hell helps when we know what vehicle we're talking about,

If you have a 1/2 ton the connector is 2 feet away from the trailer plug, just trace the wires to the 3 way connector.

And btw, you won't get a voltage drop of that amount in a wire, perhaps at the connector on the end of the wire, but not in the wire itself.
 
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As Al said, it sure as hell helps when we know what vehicle we're talking about,

If you have a 1/2 ton the connector is 2 feet away from the trailer plug, just trace the wires to the 3 way connector.

And btw, you won't get a voltage drop of that amount in a wire, perhaps at the connector on the end of the wire, but not in the wire itself.
first off its trailblazer forum so not a dodge for sure..I thought it was in my signature but no
05 lt 4.2
 

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On my 1997 GMC K1500 Suburban, its between the gas tank and the bumper. Because of corrosion issues and having a small budget I have completely removed these plugs. Instead all my wiring has been soldered and double shrinkwrapped. Good for ever.

On my 1998 GMC C1500 Sierra, it's in the same spot except theres no gas tank in the way to access it. The sierras 7 way plug uses the factory 4 way plug. Hmmm I installed this many years ago when my buddy owned it.... i cant quite remember but I think someone hacked it up and I put it back together, soldered and shrinkwrapped but with a 4way plug instead of the 7way. The 7way plugs into the 4way and the blue and orange wires which are hidden inside the oem wiring loom were soldered and shrink wrapped to the 7way. Well after looking at this just now I wanna take it all apart and simplify things.... even if it isn't broke. Lol.

So depending on what your driving it should be between the bumper and spare tire? Maybe towards the drivers side frame as this is where it runs to the back.

Gotta get down and take a look.

Al

...... it dosent matter if it's a transport truck wires are wires and brake/turn/running lights are all the same.... they all have to function the same and trailer wiring is the same. Hopefully no one has hacked up your wiring because this makes it a bit harder with plug and play parts.

Have you taken a look yet? Take some pics and post them.

Al
 

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Iv never worked on your year of vehicle. I would assume gm didnt change much when it comes to the tail light wiring.
 

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Sorry, I missed that you had listed the thread under the Trailblazer/Envoy forum.

I had an Envoy a few years ago, so I'm going from memory, but it's not as sharp as it use to be.

One thing I know for sure, the trailer connector on these trucks will get jammed up with mud on the back side of the connector, this mud will cause the pin to short to ground.

Sorry, I don't remember is the rear wiring harness runs under the truck, or through the interior.
I'm going to say the interior, but I'm not sure.

You do have a rear seat (mid-seat on the XL) fuse panel and the rear lights are fused from there. Because of that, I'll lean towards the harness being inside.

And, back to that fuse panel, I think the trailer connector may be separately fused, the trailer signals may have separate fuses.

Have you noticed water getting into your backup lights? They are behind the rear wheels and will fill with water when you driver in a rain storm.
Some clear silicone around the bulk socket opening will cure that problem.
 
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Ray, that knowledge wont be listed in any service manual. and obviously way different than my trucks.

Straight from Experience.

Your the man.

Al
 
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Thanks Al, that was a great truck, some days I wish I had kept it.
 
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Discussion Starter #16
On my 1997 GMC K1500 Suburban, its between the gas tank and the bumper. Because of corrosion issues and having a small budget I have completely removed these plugs. Instead all my wiring has been soldered and double shrinkwrapped. Good for ever.

On my 1998 GMC C1500 Sierra, it's in the same spot except theres no gas tank in the way to access it. The sierras 7 way plug uses the factory 4 way plug. Hmmm I installed this many years ago when my buddy owned it.... i cant quite remember but I think someone hacked it up and I put it back together, soldered and shrinkwrapped but with a 4way plug instead of the 7way. The 7way plugs into the 4way and the blue and orange wires which are hidden inside the oem wiring loom were soldered and shrink wrapped to the 7way. Well after looking at this just now I wanna take it all apart and simplify things.... even if it isn't broke. Lol.

So depending on what your driving it should be between the bumper and spare tire? Maybe towards the drivers side frame as this is where it runs to the back.

Gotta get down and take a look.

Al

...... it dosent matter if it's a transport truck wires are wires and brake/turn/running lights are all the same.... they all have to function the same and trailer wiring is the same. Hopefully no one has hacked up your wiring because this makes it a bit harder with plug and play parts.

Have you taken a look yet? Take some pics and post them.

Al
Okay ,I know something is funky on the ebrake feed to the trailer Ill look thanks
 

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Discussion Starter #17
Sorry, I missed that you had listed the thread under the Trailblazer/Envoy forum.

I had an Envoy a few years ago, so I'm going from memory, but it's not as sharp as it use to be.

One thing I know for sure, the trailer connector on these trucks will get jammed up with mud on the back side of the connector, this mud will cause the pin to short to ground.

Sorry, I don't remember is the rear wiring harness runs under the truck, or through the interior.
I'm going to say the interior, but I'm not sure.

You do have a rear seat (mid-seat on the XL) fuse panel and the rear lights are fused from there. Because of that, I'll lean towards the harness being inside.

And, back to that fuse panel, I think the trailer connector may be separately fused, the trailer signals may have separate fuses.

Have you noticed water getting into your backup lights? They are behind the rear wheels and will fill with water when you driver in a rain storm.
Some clear silicone around the bulk socket opening will cure that problem.
Thanks .. I dont have any moisture in the tail lights at all .
 
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