Sunday Evening Wiring Puzzle

I'm having trouble tracking down a wiring issue in my 74 cj5 with an original mostly unmolested wiring harness. So far I've cleaned all the grounds I can find, replaced a couple of bad fuses, and tightened up a few loose connections. I am not positive all of the following are related.......

The symptoms:

• no taillights
• no blinkers
• power into and out of the brake light switch
• passenger brake light works with the pedal
• drivers side brake light does not
• hazards - both front and passenger rear blink, driver rear does not but is on
• driver brake light and license plate light come on and stay on with the key, regardless of the brake pedal or headlight switch position.

In the past all the electrical problems I have had have been solved by cleaning up the ground connections, but no luck this time around.

Any suggestions? Your guys are awesome!

 

No dome light, checked all the fuses.

 

The last bullet is what stumps me, maybe a short in one of the switchs?

 

The high beam switch was my first thought, tested and compared to a new unit, no change in operation.

The tail lights ground through the mounting studs, removed and cleaned the grounds.

There is power to each light, but at different times. Drivers side only when the key or flashers are on.....passenger side though the brake light switch. I haven't tried to power each light individually bypassing the jeeps power system, a task for tomorrow.

Wiggled the bulbs with power to them, removed, tested the sockets, filaments are intact and bulbs have continuity. These are fairly new assemblies, no corrosion in the sockets.

 

At this point, I would suggest you are at the end of taking shortcuts. You need to use your multimeter or test light and methodically test step by step from one end (light or battery) back to the other (battery or light).

Indicators, hazards and brake lights are the same bulb filament, and are the same signal switched differently. I would start with the warning lights and look for why the one light does not blink. Take clear and meaningful notes. I recall everything for the indicators and brake lights goes through the turn signal switch. You could start at the blinker/flasher relay for the warning lights (presuming you have signal there) and go toward and through the steering column and to the back of the Jeep, step by step. The steering column is where the relay signal is diverted to one side or both sides.

 

This is where I'm headed, step by step testing. I plan to clear the lower wiring harness and fixtures of any wrong doing, so to speak, with a separate power source.

Then move behind the dash and trace the connections one by one. I've been studying the wiring diagram and have a decent multi meter.

I'll take your suggestion and start with the flashers. Based on the wiring diagram the brake lights go though the indicator then to the hazard switch. And the hazard switch has a separate power source when the flashers are in the on position, neither are tied to the key "ON" position.

 

Check the turn signal switch too.

 

Bad ground or a shorted ground in the lower wiring harness.

Started by working backwards from the tail/brake lights with a separate power source at the firewall. Putting along testing and labeling then found 2 hot wires with joint continuity, odd but not a deal breaker, yet. Touched the tailpipe with the multi meter and....continuity.....we'll that's not right. The same 2 hot wires have continuity through the grounds.

I don't know if this will solve all the problems but needs to be fixed before moving forward.

 

Make any headway?

 

I haven't been back to it yet, hopefully tomorrow.

 

remove hazard flasher and try the turn signals may assist in assessing what side of the system problem lies.

 

Thanks, I did determine that the short in the lower half of the harness is located where the harness is fairly is accessible, around and behind the gas tank. So it looks like I will need to pull that section out for repair. I've been down with a head cold so not much headway in the last week.