Technical Headlight Switch

This morning went to go to work and headlights didn't come on. Taillights OK. I can move the Headlight switch a little less pulled out and the yellow lamps come on but still no Headlights. Not sure if it's electrical issue or switch issue. Really don't know where to start. This is a 65 c10 and the wires are like spaghetti from years of rigging from previous owners. Thanks in advance for advice.

 

Search on-line for a wiring diagram specific to your truck and print a copy, so that you can determine what should go where. That way you should be able to rebuild the mess. Check with some of the companies that offer bits for your truck series - maybe an under dash harness is available.

 

If you are getting a better connection by fiddling with the switch for parking lights, it sounds like a dirty switch contact. But those GM switches have an internal circuit breaker just on the headlight wire, so get under the dash or drop the switch down to test with a test light.

You may be able to take the switch apart to clean the contacts, and to file the points on the breaker....if that was the issue.

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If you don't know how to remove the switch knob to be able to drop the switch out:

The knob with the long rod needs to be removed to undo the chrome nut on the dash.

Reach under and feel the sides of the switch body, to feel for a spring loaded push button sticking out of one side of switch. Hold that button in, while pulling the rod all the way out of the switch. It might take a few tries of moving the knob in and out, to feel that button go "in", then yank the rod right out

Disconnect the battery cable first

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So did the lights work before today? Might be something simple like a bad ground or a loose wire. Don't forget the dimmer switch on the floor.

 

if the knob won't pull out all the way, you'll have trouble getting the switch out! I suggest you first disconnect the battery, (yes I'm being repetitive, on purpose) then do as suggested to remove the switch, and replace it or take it apart and see if you can fix it.

But I'm also assuming it's the original switch, it might not be. often a previous owner will have been clueless and replaced it with a crappy generic switch. Hard to tell without seeing it...

 

Hi. I think you must pull the switch knob all the way out to headlight on position before that release button will go in far enough. Then with release button pushed in knob & shaft will come out.
Jimmie

 

Probably the dimmer switch - they fill full of crap the way they're mounted, & usually have damaged terminals.

 

the dimmer switches do go bad, usually they lose one side first, so when you click it the lights turn on, then click it again they turn off, etc.

But basic troubleshooting techniques would be useful.

 

Here is a diagram of the most common GM headlight switch, should be ok for a 65. Either way, check for power at the dimmer switch center terminal. If you have power there, you know it's an issue from the dimmer switch forward. If not, then the dimmer switch is not getting power from the headlight switch. The headlight switch powers up the dimmer, and the dimmer just switches back and forth from high to low on the other two terminals.

 

xx2 that was what was wrong with my 63 nova

 

Some early GM headlight switches had two 12v feeds - one for headlights and one for tail, dash, and dome lights. Your headlight 12v feed may be NG. Should be easy to check.

 

Thanks everyone for the feedback and wiring diagram. It was the dimmer switch.