Electrical Gremlin.....weird, man.

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Paul Peckham

Paul Peckham

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My 74 Dart is running like a top on Tuesday....everything works. Wednesday morning I drive her to work and the instrument lights aren't working. On the way home I get pulled over and the nice policeman tells me I failed to signal a left turn. After I tuck the citation away, I find out the rear blinkers horn, tail and brake lights are inop. And the plate light is out. And the side marker lights aren't coming on.

What the heck is goin on here ?

What IS working you ask ?
Headlights, backup lights, front turn signals and wipers. And the radio.
What circuit, relay, fuse, ground or switch do these 7 things share? Or did I have 7 things fail at the same time?
My Haynes is kinda weak in this department.
 
Check the fuses. Use a test light.
 
I looked at em and they're intact. The glass type. I only have 5 fuses in the box. Could they be popped and not show it?
 
What electrical modifications have you done?

What have you done to the car lately?


Mymopar.com has free factory service manuals and electrical schematics.

Classiccarwiring.com has colored, laminated wiring schematics, best 20.00 you'll spend.



Paul Peckham said:
Wednesday morning I drive her to work and the instrument lights aren't working
Click to expand...

Instrument panel is fed through the head light switch and a fuse in the fuse block



Paul Peckham said:
I find out the rear blinkers horn, tail and brake lights are inop. And the plate light is out. And the side marker lights aren't coming on.
Click to expand...
Blinkers, horn, tail, brake, license plate light come through the turn signal switch and a second fuse.

I would look at your fuses, then turn signal switch and related connectors.

If two fuses blew I would suspect that there are damaged wiring in your harnesses.

As for the things that are working most is not fed by the fuses in question.

NOW I am basing all this off of a 67 Dart wiring diagram, much will be the same but some will be different. Like the backup light cir might come form another source as the switching for it comes from the transmission vs the steering column or console as in 67


As for fuses.

Pull them out and check with a multimeter.

Most likely if it looks good but is blown it will come apart as you remove it.

Also some fuses are not powered on one side all the time. So e only have power when as example a switch is turned on.

I'm attaching this photo not for you to diagnose your issue just to show you what the classic car wiring product looks like

PXL_20230312_061254378.jpg
 
I have a '92 Dodge B350 van. I found out recently that when the dash lights are out and the "Idiot" buzzer isn't working the brake lights are out too. It was a broken trailer wire that blew the fuse.
 
No modifications to wiring. Hung a new driver's door last week. Maybe I knocked something loose adjusting the upper hinge. I'll check fuses first then the fusebox with switches off an on. With only five fuses in the box, there must be several circuits on each fuse. Hense a 20amp fuse for the key buzzer.
Thanks, guys. I will report back.
 
Bulkhead in the firewall where the electrical connection go to the engine get corroded, but since it is the rear lights I would think it is the headlight switch...
 
There is a wiring plug down by the lower hinge opening that feeds the rear electrical. Might check you didn't disturb something there .
 
Couple things on the fix :

It was a fuse. #7 to be precise. And the horn crapped out. And all the running light bulbs were good - just the sockets were corroded. Same with the brake lights.
Between the wiring diagrams and your experience and suggestions, I sorted it out.
Thanks for the help, everybody.
 
Paul Peckham said:
It was a fuse. #7 to be precise. And the horn crapped out. And all the running light bulbs were good - just the sockets were corroded. Same with the brake lights.
Between the wiring diagrams and your experience and suggestions, I sorted it out.
Thanks for the help, everybody
Click to expand...
Glad it was easy!
 
Had a issue like that on a 72 dart, found out later the gaskets around the taillights were leaking letting water mess with the system.fixed gaskets no more problem .just saying
 
For future reference the grounds at the tail lights(brass rings inside the housing) and the common ground wire in the trunk usually bolted to the body close to the fuel filler ruber have always been a source of lighting issues in every old a body I've ever owned. Dielectric grease and good tail light seals are a must.
 
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