I have a 2005 trailblazer with the same problem. When I first bought mine in spring of 2006, I noticed the lights would faintly blink once in a while, but just passed it off as normal. Over time the problem has increased, and started noticing voltage drops on the voltmeter on the dash. Now it has got so bad that people think I am flashing my lights at them! Voltage drops to 9.5 to 10 and back up to 14.5 in a pulsing 1 second or so rythm when the problem occurs. I took the vehicle last week to an alternator shop and of course it would not do it for them. They went ahead and replaced the voltage regulator and brushes on the alternator as everything else looked great and tested out fine on their bench, but did not fix the problem.

Something to add that I haven't seen posted yet - the problem seems to be there when you start coasting or breaking around 35-45 mph. Any other speeds it will not do it, nor will it do it with the acceleration. Has anyone been able to fix this? If it's an air pump drawing that much current, something seriously has to be wrong with it!

 

Interesting...thought mine was the only one doing that lol. 05 trailblazer when coming down the mountain at about 30 mph not accellerating the lights blink but i dont think they go all the way out maybe dim and then brighten and at the same time the voltage meter drops rapidly and then comes back up. Took it to the shop- they said the only thing they found was a loose wire? Still does it.

 

heres some good info,sounds like a bad 02 sens














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" src="http://service-gm-forum.com/techforum1/style_images/gm-forum-lang/nav_m.gif" width=8 border=0>2005 Trailblazer, Headlamps go out or dim[/align]Track this topic | Email this topic | Print this topic [/align]


-scrufy-

Posted: Jan 10 2006, 03:06 PM [/align][align=right] [/align]



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Member No.: 63
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Just curious here. I have had 2 Trailblazers in the past week whose owners SWEAR the headlights go completely out when driving, intermittently. I have seen them dim as bulletin 05-08-42-001 & related bulletins listed inside this bulletin describe as normal. All checks ok, alternator, battery, etc.
Just curious as to how many others are seeing customer exaggerate this condition as I feel these 2 are doing. Along with the headlights dimming, they are also saying the charge indicator swings wildly when the lights "go out". [/align]

--------------------

Bill King
GM Certified Service Manager
Gary Russ Chevrolet
Greenwood, SC
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natk

Posted: Jan 10 2006, 04:42 PM [/align][align=right] [/align]



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I've had one complaint on this type of vehicle for headlights go completely out intermittently. Did not duplicate, find anything, or attempt any repair. [/align]

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GM World Class Technician with 10 'Certs
ASE Master with L1
Gainesville, TX
652 is not that far away[/align]



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I just had mine back at my Dealer, he stated what I've read above.
The pump is not passing the passive test and keeps running a manual test or something like that.

He advised that 12/20/2007 there was an entry about a fix being worked on by engineering.

He stated that if I would start the vehicle, let it idle for 60 sec. it should complete the passive test and it should not re-test and cause the dimming.

I'll try it this morning and see if he's right.


Sounds like there is a light at the end of the tunnel finally....................................

 

[QUOTE=golfer;10374]I just recalled having a similar problem with my 00 Express van, it turned out to be the DRL module.

My buddy has a 2001 express with the same problem and he too thinks DRL module but we can't locate it and really not sure what it looks like because , I think , they changed it from the 2000 model because he keeps finding different pictures. Can you tell us where yours is and what it looks like . Thank you for any help you can give us .