brake and tail light fail (1 Viewer)

[brettwilm]

94 FZJ80 runs fine except when I step on the brake, the PS brake light doesn't come on--and simultaneously the PS tail light, if illuminated, goes out.

The brake/tail lights take an 1157 bulb with two filaments, one for the brake and one for the taillight. I've replaced the bulb but same problem. Tail light works when lights are on, but I hit the brake and both filaments go out on any new bulb on the PS.

Does anyone know offhand if this is a taillight control relay and/or fuse issue? Probably unrelated, but the PS rear door doesn't actuate the dome lights in "door" mode...couple PS electrical issues apparently.

Thanks,
Brett

 

[brettwilm]

Incidentally the DS brake and tail lights work fine....

 

[ajax1]

Do you have the trailer harness in there still, it is usually connected thru pass side so might be shorting out

 

[brettwilm]

I do have a trailer harness but IIRC it is on the DS. Good idea though, I'll double-check.

 

[LINUS]

Sounds like your brake light has a bad ground, then when you push 12v back there, it disrupts the ground for your running light.

I forget the local body ground point, but I'd start with a multimeter (just shows better the volts than a test light) - but you being in AZ at least you aren't fighting salt corrosion. Maybe before you even get the test light check the local ground terminal, and the 1157 socket looking for corrosion of any sort.

Do a clean & grease of those points, then re-check.

If still acts like a VW/Audi wiring harness (utter crap) - bust out the multimeter.

 

[BILT4ME]

94 FZJ80 runs fine except when I step on the brake, the PS brake light doesn't come on--and simultaneously the PS tail light, if illuminated, goes out.

The brake/tail lights take an 1157 bulb with two filaments, one for the brake and one for the taillight. I've replaced the bulb but same problem. Tail light works when lights are on, but I hit the brake and both filaments go out on any new bulb on the PS.

Does anyone know offhand if this is a taillight control relay and/or fuse issue? Probably unrelated, but the PS rear door doesn't actuate the dome lights in "door" mode...couple PS electrical issues apparently.

Thanks,
Brett

Did you ever find a solution?

@OverlandDad is having a similar issue.

94 LC
Both taillights work, but left one is slightly dim.

Step on the brakes, center light and right brake light come on, left taillight and brake light are out.

Cleaned wire end and frame area to bare metal, and reattached. Still no fix.

Checking voltage:
12.2 bolts at battery (yes, I know this is low, it's for reference.)
Only get 11.2 V at taillight socket and at floor harness 1 connector in left rear fender well.

Checked and pulled all fuses, found stop lamp 10 amp fuse partially melted, but not blown. Tightened terminals and inserted new fuse. No change.

Unplugged and replugged every connector in left rear fender well...no change.

Unplugged and replugged floor harness 1 in left driver kick plate....no change.

Swapped taillight relay with horn relay.....no change (taillight relay was hot when I pulled it.)

Pulled and checked fuses for hazard and another under hood. All fuses good.

Taillight socket is clean and not corroded internally.

Bulb is new.

I'm not an electrician, but I stayed at a Holiday inn last night.....


HELP 'Mud collective!

Next step?

I was trying to follow the EWD but not sure if we have all pages and I spent enough time in one chunk to find what should have been easy.

Suggestions and questions please!!!!!

 

[ppc]

If present I would disconnect any trailer wiring harness/converter box usually located behind the right rear trim panel to see if that impacts the testing results. Check the bulb sockets in both taillights.

 

[Tools R Us]

...
Both taillights work, but left one is slightly dim.

Step on the brakes, center light and right brake light come on, left taillight and brake light are out.
...

Most common cause, bad ground.

 

[BILT4ME]

Most common cause, bad ground.

And that's the symptoms, but where else do I look? We cleaned the frame rails center one and I cannot see where anything else would be......

 

[mingles]

If present I would disconnect any trailer wiring harness/converter box usually located behind the right rear trim panel to see if that impacts the testing results. Check the bulb sockets in both taillights.

^^^ This. Though you didn't mention it in your troubleshooting list, I am sure you have already checked and removed any trailer light converter. It seems that is the root of 99% of brake light gremlins.

Hopefully, the remaining 1% is covered by the thread below . I have read numerous accounts of the internal ground in the tail/brake light socket going bad and needing re-soldering.

Driver's Side Tail Light - Brake Light not working correctly 97 LX450

 

[BILT4ME]

^^^ This. Though you didn't mention it in your troubleshooting list, I am sure you have already checked and removed any trailer light converter. It seems that is the root of 99% of brake light gremlins.

Hopefully, the remaining 1% is covered by the thread below . I have read numerous accounts of the internal ground in the tail/brake light socket going bad and needing re-soldering.

Driver's Side Tail Light - Brake Light not working correctly 97 LX450

Thanks!

I knew I forgot to mention that the trailer harness had already been removed.

I guess maybe we'll have to do more on the socket itself and resolder.

What concerns me though, is that my voltage drop is still in the floor harness well ahead of the rear harness.

That tells me it's ahead of the taillight.

It can't hurt to solder it I guess.....

 

[Necota]

Thanks!

I knew I forgot to mention that the trailer harness had already been removed.

I guess maybe we'll have to do more on the socket itself and resolder.

What concerns me though, is that my voltage drop is still in the floor harness well ahead of the rear harness.

That tells me it's ahead of the taillight.

It can't hurt to solder it I guess.....

What happened? I imagine you know I’m experiencing the same thing on my driver side (left) brake light. Yes

 

[BILT4ME]

What happened? I imagine you know I’m experiencing the same thing on my driver side (left) brake light. Yes

@OverlandDad swapped the taillight harness on the LR taillight only (not the entire rear harness) and it works! He just did this yesterday.

Part number 81565-60241

 

[Necota]

Cool. I will try also and let you know. I have a harness in my spare parts bin

 

[jpoole]

I've seen and fixed this on a few 80s. In these cases the ground wire that is soldered onto the outside of the brake light bulb socket, either left or right, had come loose. Another version of the symptoms is that the left or right and 3rd brake lights won't work with the running/headlights on but do work to some extent with the head/running lights off.

To test for this (from memory, may not be totally accurate):
-remove the tail light housing(s), left/right not 3rd light
-remove the brake/tail light bulb from the housing(s)
-check that the black/ground wire that should be soldered to the outside of the metal bulb socket is well connected
--try to move it around first, can also have someone hit the brakes and then you wiggle it to see if it causes/fixes the issue

If this is the problem you can slide the socket out a bit along with the ground wire and re-attach the wire. Use a relatively hot iron and clean the housing/wire to help get a good connection.

 

[joshrabon]

I've had this exact same issue going on. No PS brake light when the head/tail lights are on. I've cleaned and retightened the ground screw on the frame at the tailgate as well as re plugged the tail light harnesses.. no help.

I'm not sure if the PO installed a trailer harness. Does anyone have a picture or reference about where this is installed?

My next option is buying a tail light harness and swapping it out...

 

[jpoole]

@joshrabon did you check the grounds on the tail light sockets? These aren't plugged in/unpluggable they were soldered on from the factory and they are known to come loose and cause this exact problem. See my post above

 

[clx16]

Passenger side rear corner. You also have a ground (bolt) in the middle on the body (to the left in the picture, when you are laying with your head on the pumpkin looking backwards. This is on my 96 though. so Might be different for you.