Head lamp dimming flickering

My 2005 Trailblazer has something ghostly going on.
When the head lamps are on at night, you can see them dim and brighten back up.
This happens almost continously.

Anybody got any ideas / solutions?

My dealer will only say Chevy is aware of it, but no fix!

Maybe its time 4 a battery change.. This happened on my jeep grand once.. it was da old battery expired.. yet check ur spark plugs n plug wires they may need a change n also check da alternator.. sum times it can be da main prob.

I had the battery checked, A-OK
It will happen with the automatic headlamps.
It will happen if you switch the headlamps on manually.
It will happen with the A/C on or off.
It will happen when you coast or maintain your speed.
I have not noticed it happening when I accelerate.

Any other ideas?

I one 10 block stretch, it happened 6 times.

If your interior lights including the dash lamps are doing this also , this indicates it's the charging system.

I just recalled having a similar problem with my 00 Express van, it turned out to be the DRL module.

Btw... hopefully your still under warranty and isn't it nice they're aware but no fix.

Sorry for delay
Been working too many hours
I'll be contacting my dealer tomorrow about the DRL module
I'll post an update!

Thanks Golfer

My wife's 2004 TB did this from day one. We usually noticed it when hitting the brakes but sometimes it would do it randomly. Dealer finally replaced the alternator and all is well, guess was a faulty voltage regulator.

I have the same problem on my 2005 TB, dealer it is a problem that they are aware of. He said it was caused by an electric air pump. They updated the computer software which should have "reduced by not eliminate the problem" (quoting the dealer). Situation worsened. But it's nice to know I'm not alone with this problem.

ive heard of this problem- may have to do with the AIR pump that comes on the 05's and up.
under the drivers seat area- under the car- theres some pump that draws quite a bit of current..... most likely why youre seeing the dimming

My 2005 tb does the same thing. Took it to the dealer and he said that it has to do it at their shop or there is nothing they can do. It did it the other day and the car almost stopped. Cant get the dealer to stand behind the warrenty. How Iam I to get it to do it right in front of them when it does it when ever it wants to. They wont even look at it til it does it all the time. I have bought Chev all my life and when they wont stand behind the warrenty it hard to say but maybe it is better if Toyota does take over.

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