Hot Rod Forum banner

Tail Ligths/brakes/reverse on 97 GMC truck

2K views 7 replies 5 participants last post by  dsraven 
#1 ·
Not that this is necessarily related to my other post about my rearview mirror, but my turn signals and brake lights have been on the fritz for the past year also. Started with the driver side. Blinker blinks real quickly and left brake light wouldn't light up when lights were on. Fixed a couple loose connections by spare tire under the bed, but never could get it to work properly. All bulbs are good. So I was thinking it might be the circuit board housed in the tailight housing. Some connections look kinda old. Then, about 2 months ago the passenger side started doing the same thing. Neither reverse light works either.
I don't want to just throw some new parts at it. I'm thinking of just taking it to a mechanic to fix because inspection is due in may, and it ain't gonna pass the way it is now (usually has trouble passing anyways).
 
#5 ·
seems like grounding out might be an issue. i've got several electrical gremlins right now.

Runnin'OnEmpty - by multi function switch, are you referring to the turn signal stalk? If so, then yes my truck has one. It controls: turn signals, wiper blades, hi/lo beams, and cruise control (which has never worked since I bought the truck 10 years ago).
 
#6 ·
Yes, that's the MFS (multifuction switch).
There's a good chance the MFS is faulty and
causing the turn signal problems. The brake
light circuitry also runs through this switch.

I suspect the back-up lights are a separate
problem.......Probably in the switch located
on the transmission or shift linkage.
 
#7 ·
do you think it would have anything to do with my light indicator on the dash not illuminating what gear i'm in? not even sure if that little red thing is a light or what, but it's probably been gone about the same amount of time as i've been having these other problems. it's in the dash cluster under the speedo.
i just have to listen/feel what gear i've put it into P R N D 1 2
 
#8 ·
rear lights

before you go buyin stuff,
first check the trailer plug if equipped. sometimes they can cause you grief, especially if they are wet. walmart sells a little thing you can plug in to the trailer plug, it has led's on it and that will tell you what you have powered up there.
unplug the harness under the rear of the box and do a test with a testlight on each circuit. power up the tail lights, signals and back up one at a time . use the testlight ground on the frame of the truck, then if it all checks out, plug it back in and go to the light plug in. do it all over again there. if it checks out good there then it is probably the bulb holder that screws onto the back of the light. if you have the lights on and the test light powers up on the ground wire, then you don't have a good ground. all it takes is a bad ground and the power from the powered up circuit will go through the bulb to the bulb ground, then back through the element of the other circuit in the bulb (dual element bulb) and try to ground through the other circuit.if it makes a ground through the other circuit then usually that bulb will be dim. if in doubt, leave everything connected and turn on a signal. then go back to the light and, with a test wire that is connected to ground, touch the metal part of the buld (that's the ground part) or if you have the push in style bulbs, touch the ground circuit for that bulb. see what happens. if it lights up like it should, then you have a bad ground for that light. i have found that most of the light issues with those trucks comes from the bulb holder on the back side of the light. they have a bad connection to the bulb or bad ground circuit in the bulb holder part. if you do the test at the plug under the rear of the truck and find everything works properly there then the problem lies after that.
have fun...
dsraven
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top