2004 Blazer DRL On during the day, off at night

My problem is with the Daylight Running lights. I think this is where the problem is originating. They come on during the day as designed but as soon as night falls, they shut off. I then have use of the high beams only. Shifting to low beam results in parking lights only, no beam at all. I have replaced the relay, thinking that would do it. Same result. Is this computer related? Any ideas???

DRL's use the high beam bulbs. Both low beams are probably burned out.

DRL's use the high beam bulbs. Both low beams are probably burned out.

Thanks so much Old Master!! Here is the deal. The low beams work. They work when the truck is first started and when it is light out. Otherwise, when the sun goes down, they stop and are non functional until daylight. This leaves the high beams. After dark, I have high beams, and if I switch to low beam, I have parking lights and nothing more. I am stumped. Anything you can add would be greatly appreciated.

The DRL's use the high beam bulbs, (inner bulbs) at a reduced voltage, that's why they are so dim. When low light conditions dictate, the autolamp feature turns the headlamps on and the DRL's off. If the dimmer switch is in the low beam position, and both low beam bulbs are burnt out, only the parking lights will operate. Here's something to try: Manually turn on your headlamps, cycle the dimmer switch from low beam to high beam and check the operation. If only the inner set of bulbs come on, remove both low beam, (outer) bulbs and look closely at the filaments. If both low beam, (outer) bulbs are ok, post back here and we'll continue with the diagnosis.

Old Master.....you truely are the MASTER!!! I would not have bet 2 cents that BOTH of the low beams would be burned out at the same time!!! I know that if I should have brought this in to the shop the mechanics would have been salivating!!! Who knows how much money you just saved me!! I am truely in debted to you!! Thanks OM!! :grinyes:

Thanks for the kind words. I've been around the block a few times... Glad I could help. Welcome to the forum, stop by anytime.

I'm having a simalar problem with a 2000 blazer. The lights only work when they want. All the lamps are in working order but only come on when they want to. I replaced the relay with no change. If I jumper the relay I can get the DRL's to come on. If I trigger them off and on a few times Then the lows will finally come on but wont stay on to long. Any other ideas on posible fixes? Thanks JJ76TA

Check your owners manual, I think the dome override button, if pressed twice within 2 seconds, will turn off the DRL's for one drive cycle, (when the key is turned off the DRL circuit will return to default operation).