Why did my headlights kill my car?

Hi Guys/Gals: Here's a strange electrical failure that I've never seen before. About a year ago, I began having some issues with the hi beam/low beam selection on the headlights on my very stock 1974 Duster. All wiring is factory original, but the foot operated dimmer switch was replaced two years ago with a new Echlin part (DS-112 from NAPA). I began to notice a fault that would come and go. When driving at night in high beam, the headlights would go out. When I shifted to low beam, the headlights came back on in low beam. A week ago, the high beam lights went out again while driving at night. Shifting to low beam didn't help - the lights were still out. Then they began to flicker, so I pulled over. As I pulled over, the entire car went dead. Absolutely nothing. I changed out the ballast resistor, but that didn't help. About two minutes later, I noticed that the interior lights had come back on. So I tried starting the car and it worked. As long as I drove in parking lamp only (no headlights), everything was fine. So what's going on? I learned that the headlights are not protected by a fuse, but by a circuit breaker. Is it possible that something shorted internally in the dimmer switch and opened up this circuit breaker? I suspect that once the breaker cooled down, that it closed by itself regaining electrical control of the car. If so, why would an open headlight CB kill an entire car? I replaced the dimmer switch with a new Echlin one and everything works perfectly now. Any ideas? Where is this circuit breaker located? Have I damaged anything in my electrical system? Ideas?


Check your bulkhead connector under the hood on the firewall... It sounds like your front end wiring harness is loosing it's connection with the bulkhead connector...

Also pull the headlight switch out of the dash and check to make sure the connection is tight and none of the wiring has melted part of the connector that goes on the switch... If the headlight circuit gets overloaded or bad connection, the main power wire will get hot and melt the hole in the connector that it goes into...

Next, make sure that the connector to the foot dimmer switch has good connections...


And as stated above, check your grounds to make sure they are good.. Take them apart, wire brush or scrape them with a screwdriver to remove any crud and get exposed metal, then put some dielectric grease on them and connect them...