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The headlights and front parking lights do not work on my '65 Chevelle 300 convertible. The tail lights and the turn signals work fine. Here's what I have checked:

1. The headlights are plugged in.

2. I checked the fuse panel and studied the wiring diagram. I did not find a fuse anywhere in the circuit. Did I miss it?

3. The wires are tight on the headlight switch.

4. The headlight dimmer switch is messed up. It does not click when I step on it.

5. I checked the 14 B/LBL wire at the dimmer switch with a volt meter. From the wiring diagram, this wire appears to be wire which goes from the headlight switch to the headlights. With the headlight switch in the on position, there is no power to this wire. On the plug in clip for the headlight dimmer, the plastic clip is melted off around the 14 B/LBL wire. It's hard to tell whether the melting is recent or old. The insulation on 14 B/LBL wire is otherwise okay.

Is it possible that the dimmer switch went bad and blew the headlight switch? Since the headlight circuit does not appear to be fuse protected, it is possible that the headlight switch could blow before the wire burned if there is a dead short.

I don't know much about electrical. So any advice, no matter how obvious, could help.
 

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First off, remove that dimmer switch and throw it as far as you can. Those things are one of the weakest links in the GM lighting system. They get stompped, and stompped on. The contacts internal to them wear out, either go high in resistance (which causes heat melt-down), or all out short to ground. No click is a bad sign.

Chances are that your bad dimmer switch could have damaged the headlight switch. The reason you can't find a "headlight fuse" is there is none. The headlight switch itself contains a bi-metallic strip circuit breaker. During overloads in the lighting system, it heats up and trips, when it cools it resets. If there was a short caused by the dimmer switch power connections to ground and immediate action wasn't taken, the circuit breaker may have wore itself out. Sometimes the breakers go bad simply due to age.

Your troubleshooting practice is correct. The blue wire is the common (+)12 output from the headlight switch. When you pull the headlight switch out to the 2nd click (headlights on) this wire has 12 volts on it. The dimmer switch then routes this 12 volts to either the green wire (high beams) or the tan wire (low beams), but never both at the same time. You SHOULD have 12 volts on the blue wire with the headlights on.
 

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I believe in 65 the front parking lights did not operate when the headlights were one. ie, they only are on when the light switch is pulled out to it's first click.

It's also possible that if the dimmer wire shorted that another connection or terminal burnt off somewhere else. There's more than 1 power feed to the light switch so just because the taillights work doesn't mean the power for the headlights is getting to the switch.

Peter
 
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