beckya99

I have a '99 Tahoe with a bizarre blinker/brake/tail light issue.
From the beginning:
Fast flash on the right blinker: replaced all bulbs on right rear side - no results. Replaced light assembly on rear right side & blinker bulbs (only) on left side.
Worked perfectly for 3 blocks & problem began again only worse. Turn on the right blinker and the left blinker flashed. Turn on the left blinker and the right side flashed as well as the left side of the license plate. Turn on the head lights and all rear functioning lights become alarmingly dim.
hit the breaks and the turn signal and rear hazard lights come on.
I had recently used my trailer light connector. Years ago it was problematic so I removed it, taped off the ends & double checked grounds.
Next: Replaced the flasher relay. All rear lights appeared to work as designed except fading ~badly~ when head lights were engaged. Tryied again and all worked perfectly and continued to work perfectly for about a month.
Then, while driving at night, I braked & signaled...got a fast flash again. Only this time - I have no tail lights, brake lights or reverse lights but blinkers (dimly) work.
Replaced flasher relay again...I now have brake lights but the flashers are wacked out again and if I turn on the headlights everything goes haywire again.
replaced the mulit function switch. It lasted about 30 days and all problems started again, PLUS the horn stopped working.
tested all wiring to and from lighting assemblies- all good.
removed entire trailer light assembly and all power past that point is correct appears to be fine
Have never blown a fuse
replaced the head light switch (with a used one) and all problems were the same except when pressing the brake the reverse lights came on.
Put the old one back in and back to all the other problems (sans reverse lights).
In between getting the multi function switch replaced and the problem reoccuring, battery had to be replaced and at the same time new tips were put on the cables.
And now you can add that the battery was disconnected for about 3 hours to let the computer reset and now I have no running lights, again, when the headlights are on. (big sigh)
ground wire to rear lights, stripped, cleaned and returned and another ground added.
Me, and two mechanics are at a complete loss.
Any ideas?

73shark

Welcome to the forum.

Was there a reason that you only replace the right rear and not the right front?

The symptoms sound like a bad ground somewhere and voltage is backfeeding other circuits.

beckya99

There's nothing wrong with the front lights at all. Even with the rear blinkers/hazard lights, etc., are going catiwhompus, everything is perfect in front.

I am however, waiting for O'Reilly to get my left bulb assembly for the rear later today.

I also think that I should just replace the entire ground wire to the battery. It had arced for a long time without me knowing it and the interior wire was actually burned away for about 2". The (ford) mechanic just replaced the tips (about a week after replacing the multifunction switch) - and for about a month everything was fine.......

I keep coming back to that...

Next on the agenda is the rear brake light switch under the brake pedal.

Then maybe the circuit board...Uh...RDL(?) that is up under the left dashboard.

Any other ideas?

Oh...also, because even though I haven't found exactly what my problem is (aside from that fact that it mimics a multiswitch function issue) is I'm changing the rear assembly because all the posts I've seen talk about the circuit board in the bulb assembly that commonly goes out on GMC.

I could be wrong, but I don't think there's a circuit board in the front lights, is there?

thanks!

Chuzz

Are you using the correct # bulbs? I know it sounds like a stupid question, but I had a similar problem with a Nissan truck I purchased several years ago and once I started checking the bulbs, none of the sockets had the correct # bulb in it. They were all wrong. Once I straightened out the bulb #s and got the correct ones in the right place, everything worked the way it was supposed to. 73Shark also has a good idea with stating that it could be bad grounds. Did you just twist the wires together or did you solder them? A loose body ground can wreak havoc on your electrical system. I'd check every ground I could find if it were mine after making sure the correct bulbs are in the right sockets.

beckya99

Well? If it were incorrect bulbs, the problem would have started long ago, and I've sinced changed out all the rear bulbs at least once...in some cases, twice.

Uh...he's a professional electrician and race car builder/driver...I'm pretty sure the ground he removed, cleaned and replaced was done correctly, but I'll ask.

Any other ideas, anyone?

(quick, before I just go blow it up!)

Lol

beckya99

and in a prior post...it's not RDL....it's DRL - for daytime running light (circuit board)...even though my headlights are just fine.

becky

slw210

#3 I would say it sounds just like a ground problem. Start at the battery and work your way around. You need to use a meter and check all ground wires for continuity, they will break, corrode, etc under the insulation.