Headlight issue

[Staceytillery]

I bought an ‘85 K-10 and am trying to get it roadworthy. The headlights weren’t working so I put new switch in. Still not working. Put a new dimmer switch in and they started working. Was driving the other night and they went out, park and tail lights still work. I checked the yellow wire from switch to dimmer, it’s hot but whenever I plugged it in to the dimmer it wouldn’t show power. So I unplugged all the headlights thinking there may be a short at the bulb, it didn’t affect it. So I jumped a wire across the yellow to green to make the lights come on but that isn’t working either. Is there a relay somewhere?

 

[RustyPile]

From the factory, headlights didn't have a relay.. However, one could have been added at some point in time.. The power feed circuit to the headlight switch is protected by a fusible link. If you have power on the yellow wire, the fusible link is intact, and the switch is functioning. If you lose power on it when it's connected, the light switch built-in circuit breaker is tripped. You probably have a short somewhere either in the dimmer switch switch or possibly in the green or tan wires going to the headlights themselves.

[EDIT] When shorts to ground are suspect, randomly attaching jumpers is a bit risky.. A better method is using a voltmeter or test light.