1970 Jeep M35A2 Tail light /brake light problem

[JOEDEUCE]

Heres the scoup, i turn my light switch to the on position, both the head and tail lights come on, turn signals in the rear work fine. The brake lights however are messed up. heres a side by side account of what happens when i hit the brakes, right side first, i hit the brake pedal, the running light cuts off, and no light illuminates at all . as for the driver side , the running light will stay illuminated when i hit the brake pedal, but no brake light...... any help would certainly be appreciated , thanks

 

[phil2968]

You have checked your bulbs I'm sure. That sould be first, then check all the grounds. The grounds seem to be the culprits in most cases.

 

[steelandcanvas]

To what Phil said. Remove the light housings and clean the ground contact points. There is no ground wire, the are grounded through the mounting bolts.

 

[plym49]

X2 This is the sort of problem you see when there are one or more flaky grounds.

 

[Katahdin]

Any forward progress?

Don't overlook the turn-signal controller on the steering wheel. On mine it looked like the previous owner/guard unit had fuddled with it. The copper on several wires were exposed near the connector, one of which had been pulled completely free, also several of the wires had been soldered.

Other issues I've had were from cracks and dry rot in the wire sheath which led to corrosion of wire.

 

[JOEDEUCE]

Hi guys, I fixed the issues. And all of you guys were right. First off my talights themselves needed replacing, there were wires with busted insulation and the ground wie connections within the light were toast. So the first step was to clean the tailight moutnting bracket and install new lights..... no go still. The next place I looked was the tirn signal swich, I took it apart and the contacts were fudged up and I could tell it had been worked on before, so ....I got a new one.... installed it, had brake lights on the driver side but not pass side... so backk to the pass side lght I go.... keep in mind I'm thinking ...my turn. Signals work, so I have ground.....WRONG.. when I removed the lense and looked at the light bulbs, I quickly realized the wring bulbs were illuminating even though the wires were connected properly. I disconnected everthing from the back of the light and had power, red lead on one of the power wires. And black lead on the light bracket, had power but no light when I plugged the brake light wire in. Long story short .....the **** light bracket had just enough ground to get a reading on my meter but. Not enough to power more than one bulb at a time, thus the reason why the pass tail light would go out when you hit the brake in full light mode. I shuld have checked resistance between tail light bracket and the frame . All the lights work great now. I need to wire up a relay so I can have my front marker lights on when the headlights are on.

 

[plym49]

Hi guys, I fixed the issues. And all of you guys were right. First off my talights themselves needed replacing, there were wires with busted insulation and the ground wie connections within the light were toast. So the first step was to clean the tailight moutnting bracket and install new lights..... no go still. The next place I looked was the tirn signal swich, I took it apart and the contacts were fudged up and I could tell it had been worked on before, so ....I got a new one.... installed it, had brake lights on the driver side but not pass side... so backk to the pass side lght I go.... keep in mind I'm thinking ...my turn. Signals work, so I have ground.....WRONG.. when I removed the lense and looked at the light bulbs, I quickly realized the wring bulbs were illuminating even though the wires were connected properly. I disconnected everthing from the back of the light and had power, red lead on one of the power wires. And black lead on the light bracket, had power but no light when I plugged the brake light wire in. Long story short .....the **** light bracket had just enough ground to get a reading on my meter but. Not enough to power more than one bulb at a time, thus the reason why the pass tail light would go out when you hit the brake in full light mode. I shuld have checked resistance between tail light bracket and the frame . All the lights work great now. I need to wire up a relay so I can have my front marker lights on when the headlights are on.

Glad you got it all working.

Instead of a relay, you can use a diode.

Also, I believe that someone on this forum posted a jumper you can add to the back of the headlight switch that will do the same thing.

 

[Gralmk]

I know this thread is a bit old, but I just ran into almost the same issue on an M35A2, had all power in every light except left side brake light worked, test grounds and power and swapped bulbs, everything worked, except the left brake light. I changed the directional and all is good, everything works.

 

[olly69]

I know this thread is a way old, but I just ran into almost the same issue on an M35A2. It sits a lot, the fuel shut off stuck in the off position, and I read up on it here, cleaned it up and runs great again! But now the lights won't come on#@! They were working, even installed a new turn signal switch a year ago, but now nothing. Any ideas where to start?