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2004 chevy trailblazer_lt
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Discussion Starter · #1 ·
Hey fellow trailvoys,

Earlier this afternoon, I headed out and when the sun went down, I noticed my headlights weren't working. I checked my brights and fogs and they work fine.

Any ideas what could've happened? Could a fuse be the cause?

They were both working earlier today (I noticed them coming on when I used the remote to unlock the doors). Kind of strange for them to both go out at the same time...:confused:

Thanks :thumbsup:
 

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The left and right don't share a single fuse. There is one for each side (#3 and #6). The first place that left and right lows come together is the underhood relay 46.

I could post a schematic if you have a meter and want to trace signals. Or give you some hints. But the relay may be it. Swap with the adjacent one of the same kind that runs the fan clutch. You can be without the fan for a few minutes.
 

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Discussion Starter · #4 ·
Thanks.

I'm gonna go check out those right now...

I'll come back and post what the problem was.
 

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Discussion Starter · #5 ·
Well,

Both the fuses are good. So when I switched the relays, the passenger headlight is on and the driver turn signal light is on. Both turn signals work when you try them.

Might be time for some new relays...I'll be back when I know more.
 

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A bad relay alone couldn't cause those symptoms, since the low beam relay is shared by both sides. If your low beam driver's side lamp blew with a massive short, the fuse should have blown quickly to protect the solid state relay, but perhaps it didn't, and the relay is now damaged.

You may need one new relay and one low beam lamp. I usually buy two at once because if one blows for being old, the other one is usually close behind.

I haven't figured out a way that the headlight relay could interact at all with the turn/marker lamp circuits, unless there's a wiring harness short. Let's fix the headlights first, because those are a safety issue.
 

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Discussion Starter · #7 ·
Just got back from my quest to find relays...I checked Advance, NAPA, Pep Boys...none of them have relays. NAPA is the only one who can even order them...for $49.99 apiece. Haven't ordered any yet...

I figured it would be a good idea to order 2 if I did have to order. Advance suggested me go to a junkyard...I'm not so sure because I could be getting a couple that are gonna go bad like mine??

I'm trying to avoid going to the dealer...figured it would be an arm and a leg to get some there.

If I need a new headlight, I have to replace the whole lamp, not just one bulb, correct?

Looks like I won't be driving around at night for a few days anyway...not sure the FL laws about driving with fogs only...:undecided
 

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Low and high beams are separate bulbs.

Solid state relays are a very rare failure item. I don't carry a spare, and I'm usually a nut case about carrying extras of things I think will fail.

That relay (15016745) is dealer list price of about $45. gmpartsdirect.com has it for $25. Make sure you try cross-referencing it with Airtex 1R1944. Rockauto.com (one of my favorite vendors) has that for $28.
 

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This is off of napafix that we use at work...may or may not help...good luck


Vehicle Application: 2003 Chevrolet Trailblazer 4.2L 2004 GMC Envoy XL 4.2L, Vin S, Eng Cfg L6

Customer Concern: There are no low beams or Daytime Running Light (DRL) operation. The high beams and flash to pass work fine.
Tests/Procedures: 1. In the underhood fuse box verify the HDM fuse to verify it is hot at all times.

2. If OK, then swap the HDM relay #46 with another similar relay and see if the lights start working.

3. If the lights do not work, check the Pink/White wire from the relay to the Body Control Module (BCM) for opens or shorts to ground.

4. If the wire is OK probe the wire to see if there is a square wave signal on the wire with lights commanded on.
Potential Causes: Open Fuse
HDM Relay
Wiring
 

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Discussion Starter · #10 ·
Thanks for the help, guys.

I went ahead and ordered 2 relays (from gmpartsdirect.com---thanks roadie) I know one's bad for sure, b/c when I switched them, some of the lights did work.

After I put in the new relays, if some of the lights still don't work, I'll try getting new bulbs for them.

Hopefully that's all and not a wiring problem. After the relays come in, I'll post the results.

Thanks again.
 

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Discussion Starter · #11 ·
Hey guys,

Well I had a little problem with FedEx delivering my relays to me (long story :x), but the good news is I finally got my relays over the weekend, and sure enough, it fixed the problem. Everything seems to be working fine now. :thumbsup:

Now, just for the hell of it, I wonder how this happened in the first place? If these relays are rare failures, I wonder what might have caused this....I do know that the day that my lights went out, I went through one of those drive-through car washes and I got the max treatment which does everything including the underbody. I wonder if some water got up in there and shorted something out?

Any thoughts?


Thanks guys, I've learned so much cool info from y'all over the past year that I've been a member.
:thx :thx :thx
 

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Knowing a bit about how they're designed, there's nothing short of a REALLY strong static spark that should be able to take them out. Certainly nothing a car wash would normally give out, since humidity and soap films tend to dissipate static build-up. Root cause is going to be unknowable.
 

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Discussion Starter · #13 ·
10-4 Roadie. Thanks for the help, and now maybe if someone else has a similar problem, this thread can help them out.

:tiphat
 

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headlights random on and off

I have a similar issue with my headlights on my 03Trailblazer. The headlights turn on and off at random, but the driving lights and high beams work. You can be driving down the road and "off the lights go". But the driving lights stay on, a few minutes later the low beams come back on. Any thoughts? Tks Craig
 

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This relay- I think is solid state--- and not mechanical...
But- when something like this happens--- it may be heat or cold related...
in your case-- it may be heating up and causing a failure--- cools down- and works again...
But next time it happens- get out and jiggle that relay around--- or remove and put back in... no go?... replace with the fan clutch relay...
 

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This relay- I think is solid state--- and not mechanical...
But- when something like this happens--- it may be heat or cold related...
in your case-- it may be heating up and causing a failure--- cools down- and works again...
But next time it happens- get out and jiggle that relay around--- or remove and put back in... no go?... replace with the fan clutch relay...
I will try, the lights usually go off when we are go down the road and unable to pull over. You think it could be the headlight swith?? Or I guess maybe the high/low lever on the column itself? Craig
 

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I have a similar issue with my headlights on my 03Trailblazer. The headlights turn on and off at random, but the driving lights and high beams work. You can be driving down the road and "off the lights go". But the driving lights stay on, a few minutes later the low beams come back on. Any thoughts? Tks Craig
I have had the same thing happend to me!It hasn't done in a while,but of corse you know it will start happening again!
 

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Next time it happens take a blunt object and hit the side of the dash where the cubby hole is on the drivers side, with the door open. Fixes it everytime on mine.(I use a mag lite) I have chaulked it up to ghost wiring in the switch housing.FYI sometimes you have to hit it pretty hard, not hard enough to damage the dash, but HARD.:m2:
 

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Next time it happens take a blunt object and hit the side of the dash where the cubby hole is on the drivers side, with the door open. Fixes it everytime on mine.(I use a mag lite) I have chaulked it up to ghost wiring in the switch housing.FYI sometimes you have to hit it pretty hard, not hard enough to damage the dash, but HARD.:m2:
I will give that a try. Hey, if you cant fix it with a hammer, it must be a electrical problem!!!!!!! Its just very frustrating problem. Rgds Craig
 

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I will give that a try. Hey, if you cant fix it with a hammer, it must be a electrical problem!!!!!!! Its just very frustrating problem. Rgds Craig
Try while drving on dark roads and not having fog lights :mad::hissy::bonk:
 
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