Rear taillight brake and reverse not working.

cburton17

New member
Passenger side rear twilight is not working for brake light and for reverse but does come on with headlights on and works with turn signals. Drivers side works Perfect. I tried taking the light assemblies out of both and swapping them and the same problem persists. Any good ways to troubleshoot?
 

billintomahawk

'02 2.7 T!N Freightliner
I'd start by crawling under to rear and follow the wiring to confirm it is intact and not messed with by someone trying to do a poor job of making a trailer hook up. Varmints and chewed are a second problem to check for. A corrupt plug connection at the light assembly is a third and a good place to check for power and then work forward until you find it.

I sharpened the probe on my multimeter so I could penetrate the insulation on suspect wiring. If one side works and the other doesn't its either after the split side to side or each side is separate. You need the wiring diagram.

Do you have one?
Do a search, many have been posted for tail lights.


bill in tomahawk
 
Last edited:

cburton17

New member
Yes, I found the wiring diagram as well as some suspect wiring from a previous owner. The main power line for the left (gray black) had been spliced onto with a wire that ran around the door and then into the the main power for right (gray red). When I removed the splice wire the right side does not light up at all. I tried replacing the fuse but that didn’t help so I guess it is a problem somewhere along the wire harness below. Maybe I should just run splice wires for the brake and backup as well? I know it is suspect but obviously someone before me wasn’t able to solve things the right way.
 

Bobnoxious

GONE FISHING
Curious, did you check G300 ground?IMG_4743.JPG
 

Bobnoxious

GONE FISHING
No I didn't. What is G300 exactly ? It's hard to tell from that diagram. Would the door components really have an impact on the taillights?
G300 is a threaded stud and nut to accommodate wire ground terminations associated with tail lamp electrics. Considering location, exposure and vehicle's age, most likely corroded.

Unfortunately, I have been unsuccessful determining it exact location. Solicited help from more knowledgeable members to no avail.

Here's an example in the engine compartment.
IMG_4738.JPG

Some learning material. Suggest reading last paragraph first.

 

Bobnoxious

GONE FISHING
Assuming "Marker" = Tail light.

IMG_4826.JPG
 

billintomahawk

'02 2.7 T!N Freightliner
From memory!

Look for a ground on the drivers side on the inside of the body panel below the rear door where the tail light wiring on the passenger tail light crosses to meet the drivers side wiring. Look for an eyelet screwed to the body????

bill
 

Aqua Puttana

Poly - Thread Finder
Um...

All of the lamps on the one side light unit share the same ground return including the 1157 5/21 watt Running/Brake lamp.

Do the other lights work properly?

vic
 
Last edited:

autostaretx

Erratic Member
A broken (or bad) ground connection can funnel a bulb's current to other bulbs on both this and the other side.

BadGround.png

--dick
 
Um...

All of the lamps on the light unit share the same ground return including the 1157 5/21 watt Running/Brake lamp.

Do the other lights work?

vic

yes, all other lights work. turn signal, reverse/backup, and brake lights illuminate.


disregard this post. lol. i thought i was replying to my post, almost identical thread. lol

sorry!
 
Last edited:

Aqua Puttana

Poly - Thread Finder
As you mentioned, the odd wiring that you described would have me suspecting a harness problem, or maybe a problem resulting from previous work/repairs. Some of the harness is revealed if you remove the lens unit. There is a rubber grommet that can be removed underneath the vehicle. That will expose a bit of the harness also.

I don't understand "twilight" in the OP.

vic
 

Top Bottom