Need ideas for diagnosing rear brake light issue

[SoCalTJ]

I tried searching some older threads but couldn't seem to find much. My rear brake lights are not working. Heres where Im at:

• blinkers work
• running lights work
• hazard lights work
• checked fuse behind glove box...even switched it with another one
• tested the brake light switch on pedal and its ok, I also bought a new one just in case and that didn't do it

Whats next?? What should I try?

 

[CharlesHS]

IF the problem is the rear brake lights... check the light sockets for 12V power and verify the tail light housings are properly grounded.
The third brake light has metal dime sized contacts on the passenger side just inside the cargo hatch; that power the third brake light.

 

[SoCalTJ]

IF the problem is the rear brake lights... check the light sockets for 12V power and verify the tail light housings are properly grounded.
The third brake light has metal dime sized contacts on the passenger side just inside the cargo hatch; that power the third brake light.

I'll check for 12V power but If the hazards and running lights work, doesn't that mean the tail lights are getting power? The 3rd brake light has been disconnected for some time now.

Do you know where the ground is for the rear tail lights?

 

[rasband]

What’s the issue you’re diagnosing? I may have missed it in the OP. Is it all those features work except the brighter brake light?

 

[SoCalTJ]

What’s the issue you’re diagnosing? I may have missed it in the OP. Is it all those features work except the brighter brake light?

Sorry, its the brake lights that dont work. I'll try to edit the original post.

 

[SoCalTJ]

What’s the issue you’re diagnosing? I may have missed it in the OP. Is it all those features work except the brighter brake light?

Sorry, it’s just the brake lights that don’t work. I’ll try to edit the orig post

 

[rasband]

Sorry, its the brake lights that dont work. I'll try to edit the original post.

No worries, I thought that was it but sometimes I’m a little thick and it takes a clarifying question!

Is this new? Have they ever worked? Has anything changed between when they worked and don’t?

 

[SoCalTJ]

No worries, I thought that was it but sometimes I’m a little thick and it takes a clarifying question!

Is this new? Have they ever worked? Has anything changed between when they worked and don’t?

Yes they used to work. Just stopped working on Sunday.

 

[SoCalTJ]

Now that I think about it, this issue may have started earlier than I thought. I recently added a 1" BL and I'm thinking maybe I pulled out a ground wire somewhere? Seems to make the most sense.

Where is the ground wire for the rear brake lights?

 

[rasband]

Where is the ground wire for the rear brake lights?

They ground to the tub through the bolts.

 

[SoCalTJ]

They ground to the tub through the bolts.

Ok, I’ll double check that. If it were a ground issue wouldn’t all the other light functions (hazards, running lights) be effected too?

 

[rasband]

Ok, I’ll double check that. If it were a ground issue wouldn’t all the other light functions (hazards, running lights) be effected too?

Yes, as far as I understand it. You may want to trace some wires, there’s an FSM sticky on the forum that should show you which lines are run back for the brake light vs marker. Then you could use a multimeter to check it.

 

[SoCalTJ]

Just thought of something else. A few weeks ago I replaced the multi function switch because the turn signal lever was broken. But that doesn’t have anything to do with brake lights does it???

 

[Tony P]

Did you check the blinker fluid?

 

[SoCalTJ]

Did you check the blinker fluid?

View attachment 261271

Yes, right after I checked the fetzer valve and the ball bearings.

 

[CharlesHS]

Yes, as far as I understand it. You may want to trace some wires, there’s an FSM sticky on the forum that should show you which lines are run back for the brake light vs marker. Then you could use a multimeter to check it.

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

 

[SoCalTJ]

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

Thanks, I'm actually looking over the wiring diagram now. I hate electrical stuff and really dont fully understand how to read the diagram but I'm working through it.

 

[CharlesHS]

What you need to do is have someone assist you...
Remove the tail light cover and the brake light bulb; have someone press the brake pedal and see if you read 12V to ground on the brake light bulb terminal in the bulb socket. IF not.... you need to trace the wiring back until you read voltage. The schematic in 8W will assist you in wiring colors and connector terminal numbers.

 

[SoCalTJ]

What you need to do is have someone assist you...
Remove the tail light cover and the brake light bulb; have someone press the brake pedal and see if you read 12V to ground on the brake light bulb terminal in the bulb socket. IF not.... you need to trace the wiring back until you read voltage. The schematic in 8W will assist you in wiring colors and connector terminal numbers.

Thanks, I'll give that a try later today.

 

[JEEPCJTJ]

Brake lights, rear blinkers and rear hazard lights should all be using the same wire to the same filament in the same bulbs. I'm not sure where those all connect together but since two of them still work it looks like your brake light problem is somewhere before that connection.

If you have a prior exported Jeep with amber rear turn signals blinkers there is no connection to the other lights so that brake light wire goes all the way back and I'd think the problem would be really close to the tail light housings.