NO LOW BEAMS

Worktruck · December 2, 2004

I just went to go out tonight and I have no low beam headlights, either side. It was dark when I got home and the lights were working fine, than I go to go out and no low beams at all. I haven't had any trouble with the lights flickering or anything. Kind of strange. High beams work fine. What are the chances of both low beams burning out at the same time? Ahhhhhh.

budhayes3 · December 2, 2004

Well, I've seen it happen before, but the chances are kinda slim. If the bulbs are OK, I would look into the dimmer switch.

budhayes3 · December 2, 2004

I have a shematic for a 99, I could scan and email it to you if you'd like.

GM-Tech · December 2, 2004

What are the chances of both low beams burning out at the same time?

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Chances are slim, but I've seen more than one tech on a wild goose chase trying to figure out why the headlights didn't work and it was just both bulbs burned out.

Your particular vehicle uses ground to switch on the lights. There's a right and left headlamp fuse, but those supply high and low beams, so if you have high beams, it's probably a ground issue.

The dimmer switch provides a path for the ground, but I haven't seen those go bad. Possible though. I've seen more problems in the UBEC (Underhood bussed electrical center) with connections.

budhayes3 · December 2, 2004

Just like GM-Tech said, the low beams share a common ground that goes through the UBEC...looking at a schematic right now.

Also, if you have any aftermarket electronics that involve the lo beams...alarm, remote start, etc., I'd check them also.

GM-Tech · December 2, 2004

Just like GM-Tech said, the low beams share a common ground that goes through the UBEC...looking at a schematic right now.
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If I recall correctly, I have had at least 3 that had a burned connection on the UBEC connector C1, terminal D3.

budhayes3 · December 2, 2004

Just like GM-Tech said, the low beams share a common ground that goes through the UBEC...looking at a schematic right now.
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If I recall correctly, I have had at least 3 that had a burned connection on the UBEC connector C1, terminal D3.

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C1 D3...connector on the UBEC side between the UBEC and the dimmer switch...good memory!

GM-Tech · December 2, 2004

C1 D3...connector on the UBEC side between the UBEC and the dimmer switch...good memory!

After the first one kind of beats your butt, you tend to remember these things.

Worktruck · December 2, 2004

Thanks for the input guys. I have the day off so I'll check it today.

Worktruck · December 2, 2004

I don't believe it but both low beams burned out at the exact same time. Now I just hope it wasn't due to some power surge or something. But anyway all fixed.

GM-Tech · December 2, 2004

I don't believe it but both low beams burned out at the exact same time. Now I just hope it wasn't due to some power surge or something. But anyway all fixed.

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It happens. Also, sometimes a person doesn't notice that one is out for a while... until the second one burns out and now you have NO lights.

budhayes3 · December 2, 2004

That's probably what happened, you might not have noticed that one was burned out until you turned em on and there was nothing but darkness. At least it's fixed.

Worktruck · December 2, 2004

They were both working yesterday afternoon when I pulled into the dru=ive. I park up against the garage door so it's easy to see one light out. Go figure.