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2004 chevy trailblazer_lt
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2004 chevy trailblazer_lt
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It is a quality unit. Can't wait to try it on our 2022 Silverado.
 

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2004 chevy trailblazer_lt
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It is not just this vintage of TrailBlazer. Most every vehicle built in the last 20 years qualify for this precaution. Why? Because of all the computer modules that have been incorporated into the vehicles in order to minimize emissions, increase gas mileage, make things more convenient for owners, enhanced vehicular reliability (admit it, you love not having to change points every 12,000 - 18,000 miles), etc. Because of all these computers and minicomputer modules, every now and then something gets out of whack and their controller (or computer of minicomputer module) needs to be reset in order to go back to their original factory programming.

Going back to original factory programming is fine for electronic devices, but when you start having actuators that use nylon or other plastics for gears, and those items are over several years old (and likely out of warranty), running their recalibration routines, those brittle gears begin to break, and most people really like their AC in the summertime, and when that cooled air does not come out of the appropriate HVAC ducts, or their power door locks make noise but do not lock/unlock their doors, people go nuts, and when they find out it might take several hundred dollars in labor costs to replace a single HVAC actuator that retails for say $75.00, they go out of their minds.

Now, suppose you take your vehicle in to a responsible auto shop to have the battery replaced because it is on it's last legs. How would you feel if the shop did not use a KAM device to protect all those creature comforts and after they replaced your battery, you paid the bill only to find out that now your AC does not work right and the shop says "...we did not touch the AC system so that is a new problem and we are not responsible for it..."? So, using a KAM device makes good shop sense.

To coin a phrase from a commercial I heard years ago "...these aren't your father's Oldsmobiles..." This has never been truer.

As far as manufacturers having people monitoring various forums, maybe GM does have people monitoring this and the GMTNation forums, but from what I have seen on the GM-Trucks forum, the manufacturers representatives really only pay attention to those vehicles that are under the original factory warranty.

By the way, I am sure there are other vehicle manufacturers that also use gear driven HVAC actuators rather than the old wire cable connecting wire between the dash controller and the various doors in an HVAC system.

Does this help you any?
 

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2004 chevy trailblazer_lt
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I would suggest you find a local GM dealer and ask to speak with the lead (head) technician in the service department. That individual will likely be the most experienced in the department, undergone the most GM training, and will likely be able to explain to you the reasons and rationale you seek.

I just accept that it is the way it is because of a whole lot of reasons.

Good Luck!
 
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MrGrumpy, Welcome to the Forum.

Yes, we are sure this is not some kind of voodoo. It is a real thing. Welcome to the world of computer controlled vehicles and computer operated systems. All you need to realize is that the computers/various modules control virtually everything.

Want to start the vehicle, well when the ignition key is turned to the start position, the ECM looks at the input from the various information sensors before you can even realize it and then it commands the ground circuit side of the starter relay to close, commands the ignition system to power up, and multiple other commands are sent out, and then the vehicle starts.

Want to turn the headlights on - well when you turn the headlamp switch to "headlamps on", you are actually requesting the BCM (body control module) to allow the ground sides of the headlamps relays to complete thereby allowing current to flow to the headlamps to illuminate.

Now, when the vehicle is relatively young (and likely under warranty), the plastic gears inside the HVAC actuators are not brittle and the chance of them breaking during a power restored calibration routine is quite small. However, as time goes on, the chance of a plastic gear breaking during this process increases dramatically.

This help you to understand this any better?
 

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1 - we are talking about the gears inside the HVAC actuators NOT the HVAC blend doors that are connected to the actuators.

2 - the battery supplies the power which is required for the various memories to be retained. That's why there is a certain necessary parasitic current drawn from the battery when the vehicle is shut off. You know how you have to run around your house and reset all the various clocks on appliances, TVs, etc. after a power outage (assuming you do not have a whole house backup generator)? Same principal here.

3 - it is obvious that you have plenty of book knowledge, but what about practical knowledge on how this stuff actually works once it is incorporated into a vehicle?

4 - I do not believe anyone has actually said that the internal gears inside an HVAC actuator will break every time the battery is disconnected/reconnected. What has been stated is that each time the battery is disconnected the risk of an internal gear inside one or more of the HVAC actuators increases. Using a KAM device simply allows the memories/configuration data from disappearing and hence it reduces the need to run a recalibration procedure which increases the risk of one of those aged, brittle gears from breaking.

5 - leave the engineering principles you learned in the laboratory and classroom, and learn how to use them to repair some of the nightmares that other engineers created because they were trying to impress their co-workers.
 
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