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2004 chevy trailblazer_ls
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Discussion Starter #1
Recently we began having dead battery issues. Initially, we replaced the battery, but then the new battery died while at work as well. We noticed that randomly, sometime minutes, sometimes hours after we have shut the vehicle off, the headlights come back on. This is headlights only, no dome lights, no dash lights, break lights nor any other lights come on. Used to happen every so many days, now this has become more frequent; twice this week. Took it to dealer and they could not find anything wrong and stated they have to spend much more time and our money tracking it down. I've researched online for a couple weeks and nothing I've seen quite fits.:bonk:

Has anyone run across this issue.
 

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2008 isuzu ascender
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975 Posts
Maybe check the headlight solenoids. Also maybe the headlight switch itself.
 

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2005 isuzu ascender
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319 Posts
Try the headlight control module relay in the fuseblock under the hood. Its not really a relay it is a solid state circuit/module. One failure mode can turn headlights on.

I don't remember the location # but it is a special item. You can swap with the 1 other that is identical next to it or outright replace it. It will be more expensive than a standard relay.
 

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2003 chevy trailblazer_lt
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2 Posts
headlamp going on by itself issue

I'v swapped the relay and will see if that works
I just read your post and am having a similar problem with my 04 chevy trailblazer. the lights have started coming on randomly too. I'm just wondering if changing the relay ended up working for you? your feedback is appreciated!
 

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2002 chevy trailblazer_lt
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2002 Chevy Trailblazer

.. at first the headlights wouldnt turn off they stayed on until it ran my battery dead. so i took it to Advance Auto. and they tested the Battery and alternater and they said it had a bad battery cell. so i bought a battery and put it in... 2 days later same thing except now they go off but come back on and stay on. i got home friday night at 10:30 the lights went out when i went outside at 11:30 they was on.. come back home at 12 and they went out. woke up the next morning to a dead battery. took it to a auto shop. and after more than 24 hours he called me and said he thinks its the after market alarm system. so he took it out. charged me $107.25.. brought it home and surpise surpise the headlights wont go off again..:hissy::hissy::hissy::duh::duh::duh:
 

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2003 chevy trailblazer_ls
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4 Posts
I've been having this issue as well. I tried switching the "relay" and it didn't make any difference. Finally pulled the fuses to prevent the dead battery issue while at work or at night while sleeping. Put them back in when I need headlights. Guessing it may be the actual switch but haven't decided to part with the money for that yet.
 

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2002 chevy trailblazer_ls
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1 Posts
Did the headlight assembly swtich replacement end up working? Getting under the hood to pull the fuse or disconnect battery is so annoying.
 

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2002 Chevy Trailblazer

.. at first the headlights wouldnt turn off they stayed on until it ran my battery dead. so i took it to Advance Auto. and they tested the Battery and alternater and they said it had a bad battery cell. so i bought a battery and put it in... 2 days later same thing except now they go off but come back on and stay on. i got home friday night at 10:30 the lights went out when i went outside at 11:30 they was on.. come back home at 12 and they went out. woke up the next morning to a dead battery. took it to a auto shop. and after more than 24 hours he called me and said he thinks its the after market alarm system. so he took it out. charged me $107.25.. brought it home and surpise surpise the headlights wont go off again..:hissy::hissy::hissy::duh::duh::duh:
I had this problem and on a whim took the battery out of my key fob. Problem solved.
 

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2002 chevy trailblazer_lt
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566 Posts
First thing I would check... Is it high beams or low beams? The use different relays so knowing which it is will help to track down the issue.
 

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2002 chevy trailblazer_lt
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566 Posts
Low beams are the issue
What has been tried so far? Swap relay module #45 & #46 in the underhood fuse block? These 2 are the same as each other but different than all the other relays in there. One runs the engine cooling fan and the other the low beams. If one is having an issue with either the engine fan or the low beams it is common to swap them to see if the problem swaps with the modules.

Also, in the meantime it is easier to just pull out relay #46 instead of connecting and disconnecting the battery, and likely better for the battery and the rest of the vehicle as well.

IMG_20200905_181316~2.jpg
 

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What has been tried so far? Swap relay module #45 & #46 in the underhood fuse block? These 2 are the same as each other but different than all the other relays in there. One runs the engine cooling fan and the other the low beams. If one is having an issue with either the engine fan or the low beams it is common to swap them to see if the problem swaps with the modules.

Also, in the meantime it is easier to just pull out relay #46 instead of connecting and disconnecting the battery, and likely better for the battery and the rest of the vehicle as well.

View attachment 55630
Worked like a charm, wished I would have read this Post and troubleshooting advice first! Thanks!
 
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