Brake Light not working one side

[scottofazphx]

I have a m1165 I have been restoring and have a weird issue. The driver side break light does not work. You would think its a bulb, so easy enough repair but here is the issue. The old busted up light didn't work so I order a set of incandescent ones and an LED set for after the rebuild is done. I install the incandescent and it won't light. I switch with the passenger side and it still wont light. I test the bulb and it is good. Fixture socket has 24 volts when brake pedal is engaged. Switched to led thinking maybe its the fixture and the way it build...nope still no light.

So, I bust out the multimeter and test the incoming wires. When brake pedal is engaged wire 22 has 24 volts when tested with fixture ground. When disengaged the voltage drops to zero.

So next I jumped the fixture completely and connected the bulb with jumper wires to wire 22 and ground when I know it has 24 volts and still won't light.

Any ideas? Possible to have volts but no amps? how would I even track down where to look when the other light is working?

To further clarify, the side marker and tail lights, and BO lights all work at this location sharing the same ground so cant be a ground at fixture issue!

 

[Mullaney]

I have a m1165 I have been restoring and have a weird issue. The driver side break light does not work. You would think its a bulb, so easy enough repair but here is the issue. The old busted up light didn't work so I order a set of incandescent ones and an LED set for after the rebuild is done. I install the incandescent and it won't light. I switch with the passenger side and it still wont light. I test the bulb and it is good. Fixture socket has 24 volts when brake pedal is engaged. Switched to led thinking maybe its the fixture and the way it build...nope still no light.

So, I bust out the multimeter and test the incoming wires. When brake pedal is engaged wire 22 has 24 volts when tested with fixture ground. When disengaged the voltage drops to zero.

So next I jumped the fixture completely and connected the bulb with jumper wires to wire 22 and ground when I know it has 24 volts and still won't light.

Any ideas? Possible to have volts but no amps? how would I even track down where to look when the other light is working?

To further clarify, the side marker and tail lights, and BO lights all work at this location sharing the same ground so cant be a ground at fixture issue!

.
Have you by chance checked the ground for the lights?
Lighting on the HMMWV is grounded through the wiring harness.

Where did you put your test leads for Ground?

.

 

[scottofazphx]

.
Have you by chance checked the ground for the lights?
Lighting on the HMMWV is grounded through the wiring harness.

Where did you put your test leads for Ground?

.

Yes, I tested the ground through the harness at the light. Also the other lights like turn signal and marker light is using same ground and is working at the corner. Im guessing its a connection someplace that is allowing volts but no current through. Guess ill have to start in the rear and work forward inspecting the wire.

 

[Mogman]

Does the wire 22 (I think that should be 22-461) have 24V measured when the light is attached (must pierce wire with test lead)?
If so it is a ground or an issue in the light fixture, and yes you can have a ground issue and the tail light still work as it can seek ground through the other (heavier) light filaments.

 

[scottofazphx]

Does the wire 22 (I think that should be 22-461) have 24V measured when the light is attached (must pierce wire with test lead)?
If so it is a ground or an issue in the light fixture, and yes you can have a ground issue and the tail light still work as it can seek ground through the other (heavier) light filaments.

Ill give that a test later today, thanks for the idea! Yes i meant 22-461, good catch

 

[REF]

There are 2 threaded holes on the back of the light with a flat bar between them and the ground wire under one of the bolts. If I remember correctly the mounting bar (as its called in he manual ) is what supplies ground to both bolts. do you have the mounting bar in place?

 

[scottofazphx]

There are 2 threaded holes on the back of the light with a flat bar between them and the ground wire under one of the bolts. If I remember correctly the mounting bar (as its called in he manual ) is what supplies ground to both bolts. do you have the mounting bar in place?

mounting bar is not in place but i have tried with jumper between the two bolds and if i open up the fixture (remove lens) i can see its internally jumped. Both studs go to same internal ground plate. Plus other side also does not have plate and is working as it should. But thank you for the idea, any ideas is better than what i have lol.

 

[scottofazphx]

Anyone have any idea what and where this is? View attachment 919976

 

[scottofazphx]

Anyone have any idea what and where this is? View attachment 919976

Never mind, figured it out thats the turn signal stock

 

[scottofazphx]

So for anyone else that might have this issue in the future. I did have a bad turn signal stock, but also the cannon plug internals where turned 180 degrees.