My head lights are doing some funky stuff and I replaced the light switch yesterday but it's still doing it. I would like to cleanup the ground before I replace the switch again, I've had new faulty onesinthepastonmy gmc.I'm just not sure where to find that ground, hoping someone might be able to point me in the right direction. Thanx

 

The headlights are grounded by eyelets screwed into the forward side of the radiator core support. Pull the lamps and trace the wires from the headlight plug.

Also check the floor-mounted dimmer switch. It doesn't live in a friendly environment down there on the floor pan and under the air vent which can sometimes allows water intrusion.

Btw, what do you mean my "funky stuff"?

 

Thanx I'll do that first thing in the morning. So bear with me I don't know much but I'm learning as quick as I can lol. When I turn my head light on and my truck is idling I hear a clicking type noise by the switch, and when it clicks the truck sounds like it wants to stall, my headlights flicker and my tail lights don't work and my amp tac jumps way up. If it's called an amp tax might be called voltage......see I said I didn't know much hahaha

 

'73 F250 should have an ammeter, or "amp meter" in the gauge cluster. Later trucks changed to a volt-meter, and some trucks of your vintage would have had an indicator light only. Since you said it's got a gauge, it should be an ammeter.

Sounds like something is momentarily shorting out, or at least somehow overloading the switch. There is no fuse in the usual panel for the headlights and brake lights. There is a thermal circuit-breaker inside the switch. Sounds like that's what you're hearing as the clicking, and the lights going out momentarily until it resets itself.
But why is it doing it is the big question.

Unfortunately it's way too easy to have a bad switch right out of the box, but since it did it with both, that lowers the changes. I won't say it rules it out, as the odds are too good that you got a new bad switch too.
A good place to start is just what was mentioned with the dimmer switch. When it starts acting up, can you try flipping it to the high-beams and see what happens? Normally it's worse on highs because of more load on the circuit, but curious how yours will react.

you didn't happen to notice any discolored or burned wires and/or contacts in the connector when you changed the switch out, did you?
What is the general condition of the wiring in the truck?

One thing I would do while you're messing about with this stuff is to pull the headlight connectors off of the back of the lamps and check to make sure they're clean and not corroded. Just taking them off and sliding them back on actually cleans the contacts, but if they're bad enough this won't fix anything. If just barely bad, it will help.
Same thing for pulling the fuses and putting them back in does to their circuits. Unfortunately there is not circuit for the lights in the fuse panel. But what about the instrument lights? Do they work? They do have a fuse, so check it and see.

Definitely does not hurt to check grounds, but I don't think a bad ground will overload a circuit. If anything it makes it less likely because less current is flowing through things.
The fact that your engine slogs down a bit when this happens is not a good sign. Either the alternator is putting out a higher load when things come back on, or when something is shorting out. Or the ignition is taking a hit from this problem as well.

Anyway, just a bunch of spitballing and throwing questions at you. Definitely dig into the wiring and look for any faults or deteriorations.
And, unfortunately again, you may have to get a third switch just to make sure. But not yet. Plenty of other things to check first.

This is, in part at least, the same problem that makes many of us convert our headlight system to use relays instead of putting all the current through the dash and floor switches. The relay kits not only reduce the load put on the switch, but increase light output in most cases too, because of the much shorter distance over wire between the battery and the lamps.

Good luck.

Paul

 

I had almost the exact same thing going on. Ended up being a wire that was shorting due to the sheath being worn through. Clicking headlight switch and flickering voltage. Finally isolated it to the rear of the truck by unplugging the taillght harness power lead back by the tank. That done, no more clicking and voltage drop. So dug in. Might be worth trying. Good luck.