Taillight Woes...Help me troubleshoot!

[silvrbreez]

Hey guys,

I got a situation with my driver's side tail.  It doesn't brighten.  What I mean by that is, when I have my headlights on and the tails are lit...the driver's side light goes out while the passenger side brightens.  Same issue when I put on the turn signal with the headlights on.  It doesn't stay lit and brighten to indicate the turn, but it just stays dim and then goes out...so it's like it's blinking, but it should be staying on.

I can't tell if the bulb is out or not but it looks fine.  Any chance there is a wiring problem?

Let me know if any of that makes any sense

[Irish_Alley]

OK so see if I'm got this right w/ running lights on when you hit the breaks the left side does nothing and stays on while the right side gets brighter. sound like a blown bulb since you have two filaments in that bulb one for the running lights the other for break / turn.
same deal for the turn since the turn and break are the same filament. or you have a bad ground or the wrong bulb don't ask me how i know the last one lol

[69byrd]

Change your bulb, just in case its bad and check all your grounds.

[silvrbreez]

Swapped bulbs to different sides and the problem isn't within the bulb.  It still stays on the driver's side.

I swapped complete housings too.  The driver's side housing, now on the passenger side, still has the same problem.  Swapped bulbs again to check and same thing.

I'm trying to run some new 60-76 tails and these are fresh out the box.  Is it possible that the wiring harness coming out the back of the housing is bad.

Summing it up: It's definitely a problem with the tail lamp housing and not the bulb.  Possible wiring problem?

[VileZambonie]

yes it is a parallel circuit with a common ground. Clean your connections and grounds. If that doesn't take care of the problem get a test light and start checking which connection is open.

[jefferias]

ive got the same sort of problem with my drivers tail light as well.  mine was acting up when i used turning and what not( playing with turn signal arm)  so i came to the conclusion that my combo switch was all screwed up.  i tried to replace and broke some stuff in the column haha  so i just stuffed a new/used column from an 87 and replaced my whole 84. problem has been cut down alot but still happens every once in a while- so now i looked at the wires that go to the bulb and previous owner did a splice/hack job so i thuink thats my problem--rewire it in the spring as its too cold out.  just my .002

[silvrbreez]

yes it is a parallel circuit with a common ground. Clean your connections and grounds. If that doesn't take care of the problem get a test light and start checking which connection is open.

Vile:  Thanks for the post.  Not sure if it was in response to my original post or my last post from this morning.  Do you feel that this might be the case even still since the problem moved from the driver to passenger side when I swapped position of the housings and harnesses leading from the housings?

Just wanted clarity on that.

All the terminal posts seem very clean.  I'm going to trace the ground and clean that off.  I'll see how lucky I get with the test light check...I never seem to find a good ground for my test light.

EDIT:  Just did the test light check.  Found good ground on the frame.  The harness on the truck seems good.  Tested both sides.  With the headlights on...brown wires are hot and lights test light, with the blinkers on...yellow wire on driver's side and green wire on passenger side blinks with click of turn signal.  I tried placing the bulb contacts directly on the wires coming from the truck harness.  Same things happen.  I'm still trying more stuff.  Since it is all one circuit, I'm thinking I maybe just haven't got the wires hooked up in the right combination yet...meaning black/purple from taillamp to brown/green or brown/yellow on truck.  I'm hoping I just need to find the right combination.

EDIT:  It appears as though the company I bought the taillamps from won't allow me to return any "electrical items".  Not sure if that includes the taillamp assembly, but I've got to call tomorrow about that.

Any more suggestions?

I appreciate the help.

[oldwhity]

I had a problem similar to that with both of my landscaping trailers tail lights(they look like stepside tail lights). The problem was between the bulb and the pins(sorry I don't know the correct term) inside the assembly. The metal that the pins are connected to were slightly rotated too much which caused the two boobies(the two protrusions on the bottom of the bulb) to contact both pins at the same time. This caused them to appear like the brakes were on when just the lights were on. You couldn't tell when the brakes were pressed. When the turn signal was used it looked like the flashers were on. Hope this helps or at least eliminates a possibility.

[silvrbreez]

Thanks oldwhity.  I just read your post after getting back from checking that very thing in the garage.  Seems like the contacts all touch correctly.  I tried rotating the contacts inside the housing to see if it made a difference since the bulb can only be inserted one way.  No luck there.

I'm about to go through all the possible wiring combinations to check that.

[silvrbreez]

Thanks for all the help guys.

Figured it out.  It was combination of have the wrong size fuse in the stop/hazard plug on the fuse block and the wiring combination being off.  Got it all straightened out and it works great.

Just in case anyone else is wanting to do this swap, here is the wiring combination that worked...

Driver's Side
Black from lamp to Brown from body harness
Purple from lamp to Yellow from body harness
Passanger Side
Black from lamp to Green from body harness
Purple from lamp to Brom from body harness

(your truck's body harness might be some different colors depending on the year)

[69byrd]

Glad to hear you got it figured out.