1989 Chevy %#*@ Nightmare! Need Help on Brake, reverse and running lights

[Chev97fan]

1989 Chevrolet 2500 4x4 with 4.3 L

I was driving home the other night and someone motioned to me that my brake lights were not working... I thought, "Oh, great. Its either a fuse or another brake light switch. Its been not even a year since I replaced the last one!"

I got home and noticed the "stop" fuse had blown so I replaced it. Yet I did not have any brake, running or reverse lights. I went down to the auto parts store and picked up a Borg Warner switch and installed it. The brake lights work now! (yeah!!!) .... But the reverse lights would not come on when I put the 3-speed tranny in reverse. The lights on the front of the truck were on, that is, the headlights and the orange running lights...but NO running lights came on the back with the low or high beams on.

I've taken apart the rear light assemblies, cleaned 'em and tested the electrical boards and bulbs with a voltage meter...all passed and are in good shape. .... So I took out the headlight switch from the dash and sprayed it with contact cleaner...then I reinstalled it.... Nope, problem not fixed!

I haven't pulled a trailer with that truck for about a year, so the trailer light thing-ma-jig isn't the problem?

what am I missing here? I have replaced fuses, bulbs, the brake light switch and cleaned contact points?!?! Could it be the headlight switch mounted in the dash, to the left of the steering wheel?
I really need help here!

[Chev97fan]

For those who have had the same problem, there are 3 light bulbs in each rear assembly. The only one that I can get to work is the middle one. I have even tried reinstalling the brake light switch. All I can get to work now are the hazard lights, the brake lights, and blinkers....they all come on through this middle bulb....

When I removed the trailer lights connector from the main electrical line, no lights came on at all...But upon reinstalling it, the now all-to-familiar middle light came back on! What a nightmare!!!! Ugggh!!!

I'd like to say, "a keg of Bud Light will go to the first person who correctly diagnoses my problem." Unfortunately, we might have to take a rain check on that one! LOL

[Wheeler88]

Check for a melted middle bulb socket in the rear. That will allow the bulb to twist in the socket and allowing the bulb contacts to cause all kinds of havoc. Was supposely fixed with the 89's but some old ones might still have been used. Probably a long shot but worth checking.

[jimmydager]

Also, check the ground wire for the tail lights. I was having a similar problem and it was just caused the the grounding bolt coming loose. I am not sure exactly sure where it is on your truck, somewhere on the back frame, but maybe someone will have a better idea of where to check

[Chev97fan]

It appears I have two ground wires on the frame. I cleaned one of them and still the same problem...Will try the other one when I return home...I'll be sure to let you guys know "what the heck?!"

[Chev97fan]

I have tested all electrical connections possible and found continuity. I even took a working tail lamp off a 1997 Chevy 'Burban and tried it. And guess what? Same problem!!!! So its not the tail light "circuit boards," the bulbs or fuses. Am I missing something here????

One interesting question... I've changed brake switches out in the past, and I don't seem to recall they have anything to do with running lights or even the reverse light? Is this correct?

Hmmmm....

[Chev97fan]

Problem found? ... I disconnected the negative battery cable and resumed my testing of electrical connections. Using my voltage meter I found out there is NO continuity at the fuse!!!!!! Finally, I found something not working!!!! ..What can this problem be now?.... I guess a new fuse box is what I need?

[J-Ri]

There's no continuity at the fuse to what? B+? B-?

[Chev97fan]

J-Ri, the fuse that says, "parking lamps" ... I removed the fuse and inserted both the + and - metal doo-dads from my voltage meter directly into the empty slot, and tested it with the battery cable disconnected and connected...no power to it...

I also took off the crimp for the license plate light and ran a charge to it from a pair of jumper cables and another 12 volt battery. The light came on! So I guess I have a short somewhere. I guess I may be overlooking the trailer light connections, of which all seem solidly connected...

The only way I know how to test the wiring harness itself (the part near the rear bumper, and along the frame rail before it splits into the trailer light connector, is with one of those screwdriver/awl looking meters that light up after you stick a wire with it. Sure, it may punch a hole in the wire's insulation but at least I can tape it up.

I'm about ready to bypass the entire wiring harness and rig in new wires. I am not sure of the cost, but I may soon find out! I just saw a wiring harness on Ebay for a 2000 and up Chevrolet @ $8.95, but none for the earlier years. (five days left on the auction...if anyone needs one!)

http://cgi.ebay.com/ebaymotors/ws/eB...&category=6763

Your advice is appreciated, guys!

[Chev97fan]

How I've been testing:


There are four "male" prongs on the tail light board on both the left and right sides, and four "female" ends from the wiring harness that they attach to.

Let us take the left hand harness plug/connector for example:

Turning the connector sideways, it looks like this:

x abc ....The wiring colors are in this order:

x (brown) a (green) b (yellow) c (black)

Taking the x furthest to the left, I use it as a ground and insert the negative test needle into it. From there I put the positive needle into either a, b, or c, depending on the test being performed.


My results:


(Here I am maintaining that, "no reading" means the voltage meter did not register any current, and the indicator/pointer did not move at all; and the "good reading" means the indicator/pointer went far to the right and did not bounce back to the left. In other words, either the indicator moved in one direction or it didn't move at all! There was no "in-betweens"!!!)


x plus a = no reading
x plus b = good reading
x plus c = good reading

I then repeat the process by using a, then b, and finally c as my negative/ground starting points:

a plus x = no reading
a plus b = no reading
a plus c = no reading

b plus x = good reading
b plus a = no reading
b plus c = good reading

c plus x = good reading
c plus a = no reading
c plus b = good reading


Anyone follow me now? I am no professional here -- that is obvious!

Interesting to note that anything that is coupled with "a" shows "no reading" .... Remember, "a" is the green wire!

[Chev97fan]

Problem found!!!

I had noticed the wiring harness that runs along the frame rail had four connecting wires (male end). I went ahead and checked the polarity and wrote the results down. I then compared them with the results I had from the rear tailight harness (female end). There were discrepancies in my results...big time!

a bcd

ab no reading
ac good reading
ad no reading

ba no reading
bc no reading
bd no reading

ca good reading
cb no reading
cd no reading

da no reading
db no reading
dc no reading

After my tests, I concluded I may have had a short somewhere. I took two jumper wires with alligator clips on the ends and questioned which wires to test first. I paused. I noticed the four wires connected at the male end were intact, and when connected to the female end, four wires came out, too; but the brown wire was only a few inches long -- as if it were a dummy wire.

"Ahhh!," I thought to myself, "what if someone was under my truck and hurriedly pulled on my wires from the crimp?" There were not any exposed wires showing from either end to show that a crimp simply fell off; so if one were to pull on the wires they'd separate from the crimp and hide back inside the insulation? I had a good point!

Anyways, I used a pair of needlenose pliers and exposed the wires and used the jumper wires to connect 'em...It turns out I now have a reverse light and running lights!!!!

Thanks to all who helped me! This includes wheeler88, jimmydager, and Jr-i.