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stin1974, Transmission Tech
Category: Chevy
Satisfied Customers: 765
Experience:  Chevy Transmission Tech
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2003 Chevy Trailblazer LT: 000 miles..battery mechanic

Customer Question

I have a 2003 Chevy Trailblazer LT with 62,000 miles. The oringal battery died and I replaced it with a brand new one, same type and volts. When I left my mechanic I noticed that the idle dropped lower then usual when I stopped at a light. I then turned on the A/C and no cold air would blow out of the dashboard vents! Cold air was blowing out of the defroster vents on the front windshield,floor vents,side window vents and the rear A/C vents.I tried moving the control knob around to all positions and all fan speeds but no change.My mechanic said maybe it was the computer and the A/C would reset itself in a couple of days.I asked a service manger at a Chevy dealer and he said it has nothing to do with the battery change and it was just a coincidence .Can you tell me who I should believe and how do I fix this problem? Sweating it out in NY!
Submitted: 9 years ago.
Category: Chevy
Expert:  stin1974 replied 9 years ago.
Are your heat and air controlls electronic?
Customer: replied 9 years ago.
I dont think so. I would I know for sure?
Expert:  stin1974 replied 9 years ago.
I just meant if your gages for it are lights instead of knobs. Like climate controll type lights, if youve ever seen them.
Customer: replied 9 years ago.
I push in a button to engage the A/C and it lights up. I also push in a button to engage the recycled air flow and that lights up. I adjust the speed and vents with turning the knobs.
Expert:  stin1974 replied 9 years ago.
Have all of the fuzes been checked?
Customer: replied 9 years ago.
Expert:  stin1974 replied 9 years ago.
I would chech all of your fuses being that the battery was just changed. And if your mechanic said it was a possible computer problem, well , the computer runs off of electricity (the battery) so anything is possible as far as bumping a wire or shorting out something when removing it. But who can say for sure. But, as I said I would check the fuses first.
stin1974, Transmission Tech
Category: Chevy
Satisfied Customers: 765
Experience: Chevy Transmission Tech
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Expert:  Steve replied 9 years ago.


This is NOT a fuse or power supply issue, if the control head is lighting up at all. Also, neither the vehicle's powertrain control module (drivetrain computer) nor body control module (body computer) is involved in HVAC airflow operation so neither of these components can be the source of your problem.

Your problem is most likely an internal problem in the control head assembly. To determine this for sure, a Vetronix Tech-2 scan tool will be required to check the operation of the control head and it's ability to communicate on the vehicle's data network.

It does not matter whether the system is manual or automatic control; the same problems occur with both versions. The affected components were used in production on vehicles built between mid October 2002 and January 2003. If your vehicle was built within this date range (date of build will be on a label inside the driver's door jamb area or on the drivers door) then yours has one of the control heads that has some serviceability issues. Part numbers of the affected control heads are 15202099, 15202100, 15202101 and 15202102.

These particular control assemblies can lock up and become non functional if they receive a voltage spike (such as when disconnecting or connecting a battery cable or by jump starting the vehicle). They are also not able to be programmed at a GM dealership with new software, or they lock up and stop operating (see GM technical service bulletin #03-01-38-003).

To determine for sure if the control head has become inoperative, you will need to take the truck in to either a GM dealership or to an independent shop that has a Tech-2 scan tool to have it checked. Replacing it with a new one also requires the Tech-2, to install the correct software calibration for your vehicle or it will not operate, so I am afraid this is one of those things you cannot fix yourself at home in the driveway.

I hope this is helpful; if so, please click my accept button... thanks!