Headlights work intermittently
 

2002 Suburban 2500 8.1 liter engine. Headlights go on sometimes but not others. Doesn't matter if I use the switch or it's dark outside and they are supposed to go on automatically. Seems totally random. When I use the switch the DRL do go off so I know the switch is having at least that much effect. There is one relay but two seperate fuses (right and left lamps).
Any suggestions?

What does that mean? Is that a replacement switch? It's not the type I have.

Is the relay getting the 12V signal from the switch and is there 12V to the relay contact before the switch is turned on?

Seems both of those things would have to be happening. At least the times when they work. I'm trying to figure out where it could be going wrong. But no, I haven't tested anything. I was hoping someone had the identical problem and I'd get lucky with an answer. For them to ever work there has to be no permanent or constant problem with the switch or relay. And it's both sides so it's not lamps or fuses.

It was both meant to be real and a bit of a joke. I was born in a time when such automation in vehicles was not commonplace. The unit you see, is a separate headlight and tail/front light unit that was intended for manual use only with no automation at all. You pull it all the way out for headlights/and warning lights and half-way for tail and front signal/yellow lights only, rear tail lights only.

If my headlights fail I will convert them to such a unit but they are manual now. I run every vehicle I drive, be that an M/C, light duty vehicle or semi-truck at all times lights on. That said, you likely have an issue with a relay or the device or unit that senses daylight. You may even have an issue with the ECM. I would install this unit rather then the ECM, should my vehicles cause any similar issues.

I do not need a vehicle that runs everything through the ECM, and will keep my 1998 K-1500 running until I die. Its designed to be simple, which I like. There are no power windows or mirrors and no cruse control and no power locks. The transfer case is manual only with direct input from the floor mounted shifter only. I have no need for the front axle being nothing but solid with manual locking hubs, but it came with the suspension it did and no changing that at all. It would be too expensive for that to happen.

Manual switch over rides daylight sensor day or night. Since I don't really know how that is wired I can't say it's not the problem.

I agree that bypassing the existing wiring may be an option on this vehicle.