I got a 99 blazer. This problem is weird and I cant figure it out. During the day my head lights are on and working fine, but at night my passenger side low beam wont come on. but during the day its on. theres no shorts in the wiring going to or anything i had it checked by 2 different mechanics and they couldnt find out the problem. so if anyone can help me here thatd be cool

 

If it is like earlier Blazers, there are three relays in the glove compartment behind a plastic cover that says 'relay access' on it. One of those relays is for the daytime running lights. When I had pulled the relay to try to disable the daytime running lights, I had the same problem you describe, so that is something you might want to check. I can't remember which of the three it is (I think maybe the one on the right), but they are interchangeable. The other two are for the horn and the fuel pump. So if it is a bad relay, you can swap the horn and DRL relays and live without the horn until you get a replacement.

 

Well i went to another mechanic to have this checked and he told me i needed a new headlight assembly because mine was broke and my lights wouldnt work at because my head light bounces around which made no sense because they wouldnt come on even if i didnt move. But I took it into my own hands and looked at it and i found out my low beam socket was burned out and so was my high beam socket. so i went to pull-a-part and got 2 sockets for 50cents and a headlight assembly for 20 bucks. and it wasnt my assembly creating my problem it was the sockets but my assembly was broke so i replaced it anyway.

 

is their a reason why the running lights work but my left high beam doesnt their the same socket and bulb, i even repaced the bulb still nothing? i have a hard time understanding the workings of it.