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Discussion Starter · #1 ·
I have a 2007 TB LT and often try to do my own work.
I have read many posts here about how one should NOT disconnect the battery when doing anything electrical.

I experienced this problem just after buying my TB...it needed a new battery (who'da thunk that...a used vehicle needs new battery).
Anyway, replaced battery, re-hook everything up, now my HVAC system is all gummed up.
So, I start reading this forum and discover this vehicle appears to not do well when the battery is disconnected from the system.

The main question is: What do you guys use to maintain power to the system/vehicle so the HVAC doesn't break/need recalibration after disconnecting the battery?

For example, if an alternator needed replacement, one should disconnect the battery...but my local shop is getting tired of me coming to them and saying...uh, can you reprogram my HVAC system again because I had to disconnect my battery?
 

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Premium Member
2002 Chevrolet TrailBlazer LTZ 4.2L
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401 Posts
A KAM module is your best friend when it comes to doing stuff like battery changes. Removing the fuse of the thing you are working on instead of disconnecting the entire battery is the way to go. Some applications won't allow for this, but then you have your trusty KAM to keep this from happening again.

The rear fuse block under your seat has the fuses you need for the HVAC system. Remove them for about a minute with the vehicle off. After a minute, put the fuses back in, start the truck and leave it alone. Don't touch the controls, adjust the heat, anything. Let it run it's thing for about 2 minutes. At that point you should be good to go or you've discovered a bunch of new clicking and the reason why we don't disconnect the battery.
 

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Discussion Starter · #3 ·
Regarding the KAM module, do those cheap ones that only use a 9 volt battery work, or is there a better brand to get. I just did some brief searching and found some are pretty high in price.
 

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Premium Member
2002 Chevrolet TrailBlazer LTZ 4.2L
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401 Posts
I'd avoid that like the plague. @Ravalli Surfer knows better than me when it comes to these KAM machines and I would hope he chimes in at some point. I'm looking to get one myself, so I'm right there with you.
 

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'05 Chevy TB EXT
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5,642 Posts
Regarding the KAM module, do those cheap ones that only use a 9 volt battery work, or is there a better brand to get. I just did some brief searching and found some are pretty high in price.
Don't bother with those 9V battery devices --- they may fail you when they go dead if you accidentally open a door or turn on something that pulls them to zero.

Use a real KAM so you don't lose the settings. Although this isn't QUITE your problem, using the KAM of your choice is pretty much the same..... as long as it's not a 9V battery .........

Once you've busted the gears in the control modules, you're screwed ... there's no reprogramming available to fix that.
 

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Discussion Starter · #10 ·
Here is what I ordered from ebay.
Automotive Computer Memory Saver KaStar Hand Tools / Lang 294A
KaStar Hand Tools
Computer Memory Saver
with 120V Conerter
KaStar / Lang
294A

Made in the USA
Motor vehicle Font Transparency Vehicle Advertising

This tool is new / old Stock in the retail package.


Features:​
  • Maintains necessary power to vehicle computer to prevent loss of pre-programmed settings and or driveability codes
  • Prevents memory loss to digital radios, clocks and keyless entry systems
  • Maintains power source to anti-theft radio/stereo systems when battery is disconnected
  • Easy to use, plugs into cigarette lighter and converter end into 120V outlet
  • 6 Foot power cord
  • Buily-in LED light assures contact
  • UL Approved
 

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2004 chevy trailblazer_lt
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3,229 Posts

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Premium Member
2004 chevy trailblazer_lt
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3,229 Posts
It is a quality unit. Can't wait to try it on our 2022 Silverado.
 

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2007 chevy trailblazer_ls
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69 Posts
I have a 2007 Trailblazer and I've disconnected the battery several times this year for one type of maintenance or another and haven't had a problem with the blend doors.
Maybe I've been lucky, or the truck wasn't built on a Monday or a Friday... 😉
 

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2002 chevy trailblazer_ls
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19 Posts
I have a 2007 TB LT and often try to do my own work.
I have read many posts here about how one should NOT disconnect the battery when doing anything electrical.

I experienced this problem just after buying my TB...it needed a new battery (who'da thunk that...a used vehicle needs new battery).
Anyway, replaced battery, re-hook everything up, now my HVAC system is all gummed up.
So, I start reading this forum and discover this vehicle appears to not do well when the battery is disconnected from the system.

The main question is: What do you guys use to maintain power to the system/vehicle so the HVAC doesn't break/need recalibration after disconnecting the battery?

For example, if an alternator needed replacement, one should disconnect the battery...but my local shop is getting tired of me coming to them and saying...uh, can you reprogram my HVAC system again because I had to disconnect my battery?
One thing that has always worked for me, regardless of the vehicle: turn everything off, open the door wait for at least 10 minutes, remove the bad battery, replace it with the new one. Nothing should not work, I have done that with TB, Acadias, Fords, Audis, BMWs, never an issue, hope that helps.
 

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2007 chevy trailblazer_ls
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69 Posts
One thing that has always worked for me, regardless of the vehicle: turn everything off, open the door wait for at least 10 minutes, remove the bad battery, replace it with the new one. Nothing should not work, I have done that with TB, Acadias, Fords, Audis, BMWs, never an issue, hope that helps.
Some cars won't put all modules to sleep if a door is open. The Trailblazer's BCM computer will turn off the interior lights to save the battery, but it won't necessarily go into sleep mode. You can verify if it goes to sleep using an ammeter, it should draw less than 50 milliamps.
 

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Premium Member
'05 Chevy TB EXT
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5,642 Posts
DO NOT DISCONNECT THE BATTERY UNLESS YOU CAN KEEP THE VOLTAGE AT OR VERY NEAR BATTERY LEVELS AT ALL TIMES.

I'd believe in leprechauns or unicorns in pink and blue before I'd believe that you can just disconnect the battery and get away with it --- not for long anyway.

This ain't any other car --- and ALL GMs have the same actuators and they will die and need to be replaced when they strip the plastic gears.

That's ALL GMs of this vintage and newer.

You MIGHT have gotten away with totally killing the battery - but it'll bite you in the a$$ someday and you'll hate taking the dashboard apart to fix what you ignorantly do to those actuators.

Use a KAM or eventually suffer the consequences.

The tooth fairy is real however.
 
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