Let's fix my non-op headlights

[jayoldschool]

Ok, after two years of having my truck in operating condition, it's time to fix the headlights. They don't work.

Diagnostics:
- parking lights work
- no high or low beams
- no blown fuses
- all other wiring works

Today, bought a new dimmer. The old one came apart when I tried to unplug the harness. Took this as a good sign. Had to really work the connector to remove it from the old terminals (that were totally rusted). Grabbed the multimeter, no voltage on any of the terminals. The terminals on the wiring side aren't rusty like on the dimmer. Wait, should I have measured to ground? I didn't do the jumper test yet because the new dimmer didn't work. Does it need to be screwed to the floor to function?

I know I'm missing something simple. Thanks in advance for any advice.

On a more positive note, we fired the engine in my buddy's 63 C20 for the first time since swapping it in. Had to buy a voltage reg and horn relay to wire it up.

[lumpy63]

Sounds like you need to check your headlight switch, power goes through H L switch to dimmer switch. with the H L switch in on position you should have power to one of the terminals at the dimmer.

[Wrenchbender Ret]

The center term on the plug should be hot, measuring from the term to ground. The dimmer switch does not have to be grounded to work. The large red wire on the headlight switch should be hot all the time.

[padresag]

sometimes it is the connector at the rad support that cause a problem
ron

[jayoldschool]

Thanks, guys. It was raining and cold when I was working on it, and dinner was on the BBQ. I was definitely not at my best. I have a test light in my box to make this easier.

To do:
- center to ground to check for 12V (if yes, jumper both sides to test high/low)
- check red wire on switch for 12V (then test other terminals, actuating switch)
- check rad support connector

Tune in tonight for a nice picture of my truck with the headlights on! Hopefully ;-)

[raggedjim]

I'm with Lumpy, I vote switch.

Good luck, Rg

[scoot_mcgrute]

Originally Posted by padresag

sometimes it is the connector at the rad support that cause a problem
ron

When my headlights just up and quit on me, it was the rad support connector. I kicked myself for not thinking to check that.

[vince1]

Of course you have to get the power to the lights but don't overlook the grounds at the headlights. They are woefully inadequate at about 18 ga. and rust also plays a big part in losing them. The likelihood of two grounds being bad though would be minimal.

I did the headlight relay modification. The way it was the old way I was scared to drive it at night.

[Palf70Step]

If the park lights work, then you switch has power. Next as mentioned is the power leaving the switch. Grounds for the headlights can also be the issue. Although it sounds crazy, don't forget to see if the bulbs are OK. I beat my head on one car and it turned out both bulbs were bad.

[jayoldschool]

I still have one T3...

[jayoldschool]

Promised an update:

Lights work! Highs and lows. It's the connector that was plugged into the old rusted dimmer. The contacts are corroded enough that voltage won't pass. I can wiggle the voltmeter probe enough to get 12V on the middle terminal, but using a nice 14ga jumper between that and the other terminals gets me nothing. So... I got out jumper cables, hooked one to pos, and used that same little jumper to connect to the rad support connection. Light! Highs and lows.

I'll get a pigtail tomorrow. If it was nicer outside, I'd be out there right now just using three crimp connectors.

Thanks for helping me talk this one through. One little thing that will go a long way to making my truck more functional.

[jayoldschool]

One last update. Cut the old connector off, wired it up with new connections, hooked up the dimmer, and everything works fine. The left mounting screw spun the mount, so I'll deal with that tomorrow. I will try with front and back vise grips, but I bet the grinder will come out to play.

Next up, carb rebuild! I have zero accelerator pump action.