'74 Headlights/Brake Lights Not Working

1974 CJ5 360 convert from a 304.

Jr was driving the Jeep and both were working-next thing he goes to stop and not headlights/brake lights.

There was a 9amp fuse blow under the dash off the switch. - FIXED/Replaced

A 15amp blown off a purple wire under the hood going back to the rear tail lights or trailer harness. - FIXED/Replaced

All other fuses under the dash are good.

NOTE: Blinkers and hazards/4ways are working-just no headlights/brake lights.

Question-can it be the headlight switch?

Thanks again for the help,
Jim

 

head light switch,brake light switch,bad ground...

 

Not sure I understand why the brake light switch would cause the headlights not to work etc.

Where is the main ground for the headlight/brake lights?

Weird that the blinkers and hazards work.

Sorry, don't know much about the '74 wiring system.

Thanks,
Jim

 

not sure on a stock one.mine is all glass everything is grounded to a common point. sounds like a bad ground somewhere

 

Thank you-it's just weird that the brakes work/hazards if a ground if bad but then again I don't know how this is wired.

 

The '74 wiring diagram is at http://oljeep.com/gw/74_tsm/22-7-CJWiringDiagram.pdf - trace it out.

Grounds are typically run through the body sheet metal, with as little wire as possible. So your lights will be grounded from the bulb plug with a short wire to the body.

Loss of grounds can have funny effects on these circuits, when the current back-feeds through other components to the nearest ground. If you are curious and determined, you can probably figure it out. But I would redo the grounds first and see if the problem goes away.

 

Thank you, I'll look at the link.

Thanks for the info/short wire to the body.

Jim

 

the fact that the directional and hazards work but not the brake lights points to the brake light switch, as they both use the same filament on the bulb .and run through the same wire...check the dimmer switch too. the headlight switch feeds the dimmer and the dimmer chooses which wire gets the voltage. wouldnt have gone swimming with the jeep prior to the failure? ive killed a few dimmers that way.

 

You didn't say if the tail/marker lights work. The turn and 4-way will be powered by a different source. Stop/park-marker/tail/headlights all powered by headlight switch. Make sure harness plug is seated solid into the switch.

 

Not submerged for now LoL.

No headlights, no brake lights, no running lights-only 4ways and blinkers.

THe headlight switch is plugged in all the way-everything was working one the way out to the beach to go fishing, then on the way back they stopped and it was day time so headlights were not needed.

Maybe we will try to find a switch and go from there.

I sent him the wiring diagram (thank you) and we will look.

Just like the circuit is out or ?

He said the engine sounded funny then went to normal whatever that means.

Thanks again,
Jim

 

sounds like something shorted out ,burning the fuses,and possibly the switch or switches the wiring diagram will help

 

Found two wires going across the rear of the frame/crossmember to the passenger side tail light. The insulation was worn off.

I originally pulled the brake light fuse off the pedal indicator but it was not blown (SHOULD HAVE TESTED IT), then I tested it and no continuity.

Fixed the wire coming out of the cloth loom and replaced the fuse and everything works.

Thanks again for the help,
Jim