Need some help here. I picked up a 02 blazer and am trying to get it legal to drive. right now I'm chasing the low beams not working.

What I am seeing is 12v at both terminals at the bulb.

The high beams work and so does the indicator on the dash.

The multifunction switch seems to be working.

The headlight relay in the underhood fusebox seems to be working.

I have not found any fuses blown.

From what I can tell is there is a problem in the ground side of the bulb wiring.

Does anyone have a good schematic of the headlight wiring so I can trace the circuit?

Also is there another relay or anything else on the ground side of the circuit? it acts like there is something controlling the ground.

 

Dang man, I didn't know you were getting your info from here. I just saw this. For anyone that was curious about what the problem was. The Multi-Function Switch had burned up some wires. I had it replaced and it solved the problem. We were unknowingly asking for the same Blazer.

 

That's right you bald SOB, when all else fails ask the other knuckleheads out there. Too bad no one had anything to say on this one.

 

2000 gmc jimmy here. same issue, low beams intermittantly dont work and when they're not working there's 12V at both pins of the plug for the bulbs. high beams work, fog lamps work, daytime running lamps work, but when the low beams are turned on either via the switch on the dash or by darkness (auto light sensor), they intermittantly dont work. have replaced the headlamp ground relay and the multifunction switch and still having the same issues.

 

Just wanted to update this that I found the problem and hopefully have fixed it. The problem was on the ground side, more specifically on one of the connectors on the bottom of the underhood fuse block. Connector C1 pin F4. It's circled in black sharpie on the picture of the wiring diagram I attached and you can see the connector is burned brown around that pin. Ignore my other doodling on the wiring diagram, I had to do all that while I was probing and chasing wires to keep track of where I was at. The picture of the connector doesn't really do it justice how hot it looked like that pin had gotten.

Anyways, the female socket in the connector wasn't squeezing the male pin in the fuse block very tight and after 15 years/220k miles it started to lose contact and intermittently arc out. I sanded the male pin on the fuse block to get it shiny again and bent the female pin some so that it was a tight squeeze to get the male pin in there again and sprayed everything down with some connector cleaner. I now have solid ground through the fuse block again and so far the low beams are working.