Tail Light Problem

[TahoeTrey]

I have a 1999 Tahoe LT 4wd 5.7Vortec

I've been searching the forums for a possible answer to my problem but only found things close to what I'm dealing with.

My brake lights function fine(when pedal is pressed), turn signals work, hazards work, third bar works. But at night when I turn my lights on there are no running lights on my tail lights.

Bulbs are good. Headlight switch is good. I discovered that Fuse 9 labeled Crank has no power at all going to the circuit where you plug the fuse in.

Any help is much appreciated.

 

[tonymac617]

I believe that the bulbs in your tail light assembly are double filament. One is for when you hit your brakes, and the other for when your driving at night. Check closely the bulb and see if one of them is broken or burnt out.


The fuse situation im not sure about, but im sure someone with more knowledge on that year will know and answer soon.

 

[clkelley]

Welcome to the neighborhood!

I would have to guess that Tony is right about the bulbs, how did you check them for functionality?

I will see if I can hunt down an answer for the Crank fuse issue.

 

[TahoeTrey]

Well, i tried each bulb in the assy to see if one was blown and they all seem to function correctly also i have installed a new headlight switch as well

 

[TahoeTrey]

The way i tested the bulbs, i put each bulb in the socket that lights up when the brake is pressed. Each bulb lit up as they should which is why i believe they arent blown.

 

[clkelley]

Did you replace the switch as a result of this issue? Do you have your other running/parking lights?

 

[TahoeTrey]

Well i tried the switch to see if it worked with new switch and it didnt so i put the original back, when i test the cable that plugs to the tail light strip, only one wire has power to it. There are 4 a yellow,black, green, and brown. The green is the only one that shows power. Also tested the sockets and the middle one had no power the other two did. And yes I do have every other light working other than the tail and tag lights at night.

 

[clkelley]

hmmm. That is odd indeed. let me do some more checking and see if IC an narrow things down a bit. Sorry I don't have a direct answer at the moment.

 

[TahoeTrey]

Yeah its very weird, and I dont know if the crank fuse has anything to do with it, truck runs fine and everything, just the lights are my only issue. Thank you for taking the time out of your day to try and help me though!

 

[clkelley]

Ok, I made a call to a friend who is a Chevy master tech and he said that if you do not have power to the brown wire in the plugs for the lights, then there is more than likely something wrong with the lighting circuit board inside the light housings themselves, OR in the wiring somewhere. The green and yellow wires are for turn signals, if I am correct the green is for the left and yellow for the right side. You may want to check for something not grounding properly at the light housings, it just strikes me as odd that boths sides are effected, but he said he has seen that before.

As for the crank fuse, you won't have power to that circuit at all until the ignition is in the crank position. So you are good there as I assume you checked it with the key off?

 

[TahoeTrey]

Tested that fuse both running and not running no power to it. Ill see about trying the circuit boards and see if that fixes it, hopefully that's all it is, i dont wanna have to get all into the wiring

 

[Andrew99Tahoe]

Has anyone messed with the wiring harness? I had a 94 Suburban where the previous owner tapped into the harness for trailer lights. I had a similar issue. I replaced the harness the runs under the rear bumper to the lights and it was fixed.

 

[TahoeTrey]

no im only the 2nd owner of it nd my mother wouldnt have fooled with it

 

[clkelley]

That is good advice there. But as for the crank fuse, it will ONLY have power while cranking, not while running or while the key is off. It is only a cranking fuse. It will not have power while the engine is running.

 

[TahoeTrey]

Ok thanks alot, I spoke to a mechanic i know, he has some of the light circuits at his shop, im gonna see if that may be my problem.

 

[TahoeTrey]

Update: I fixed the issue! The under the left rear area, there's a wire harness that connects to the tag lights and tail lights, one wire had broke, guessing from heat or rubbing, but we bypassed the connector and voila it works!

 

[clkelley]

OUTSTANDING!!! I figured it was a wiring issue, but glad ya'll got'er fixed!!!

:grd: