Vehicle: 2000 Chevy S10 Blazer LS

I am having trouble with my headlights or possibly DRL sensor.

During the daytime the headlights and indicator lights are on. At night only the indicator lights come on. If I override the DRL by pressing the dome light button 4 times and turn the lights to headlights I don't even get the indicator lights. If I put a LED flash light on my DRL sensor the day time running lights come on but they are not powerful enough to see the road.

I replaced the headlight relay and it didn't help. I took it to a mechanic who diagnosed the problem as being my DRL sensor. They changed it and it worked for one night.

Any idea how to determine where the issue is with my headlights?

Thanks
Melanie