Headlight dimmer switch
 

My headlights only work when high beam is on (68 c10 truck), so I replaced dimmer switch hoping that might fix the problem. Did not fix the problem. Truck has been a work in progress for over 2 years and has the same headlights as when I bought it 2 1/2 years ago so not sure if they even worked at that time. If high-beams work, would that alleviate a wiring issue? Could both headlights possibly be bad? I know very little about wiring, so not sure how to rule out wiring issue. Thanks

Re: Headlight dimmer switch
 

Get a test light & start traceing. Check the connector on the dimmer switch. They are known to corrode in the harsh invirenment they are in. It is very possible both bulbs are burned out on low beam.
George

Re: Headlight dimmer switch
 

As Wrenchbender said the dimmer switch wiring is problematic. I had a similar issue with my Burban. A PO had cut the plug off the wiring to the switch and replaced it with slide terminals. I replaced them and the switch as they were a little crusty and when I tried removing them from the switch one of the lugs broke. All was repaired I though but nope! Still had intermittent lights. I ended up finding a splice in the wiring about a foot from the switch that was also bad. So everytime I kicked that spot it would affect the lights.

Re: Headlight dimmer switch
 

First thing is to check the lights them self. Take the connection loose at the lights. Put your test light in one fitting and see if it lights up. Then hit the dimmer switch see if it goes out. Then put the test light on the other side and see if it works. If both works then the light is burnt out.
If one doesn't work then go to the dimmer switch and try it out the same way. You could have a bad splice some where in between the light and dimmer if both of them checkout ok. Also check the grounds beside the head lights and clean them good.:chevy:

Re: Headlight dimmer switch
 

I used to have this problem a lot before I rewired the whole truck. The right headlight is worried through the left headlight. If the connection in the left headlight is bad, both lights go out, food for thought.

Re: Headlight dimmer switch
 

Yes, im pretty sure its the wiring. Went to trouble shoot and headlights were working .... now brake lights aren't. Just old wiring and need to break down and rewire the whole truck I guess.