I have a 2003 trailblazer and am having problems with the air conditioning.
When I first start up the car if the air conditioning is cut off, as long as I turn
it to #5 it works fine, then if I start driving, it will keep on running. But if I
attempt to change the air to any other level while the vehicle is in motion it
cut off completely (no air at all). The only way I can get the air back on is by
turning off the vehicle, taking the key out, starting the vehicle up and putting
the air condition back on level #5.

The only visible problem to me (besides the air condition problem) is the three
lights that are on the console that are lit up which are the:

(1)
"Parking break" lite even though I have the parking break completly down
(2)
4 Wheel drive lite, even though I'm not using the 4 wheel drive
(3)
1 other lite, can't remember what that is right now, away from the vehicle...

Any thoughts out there are appreciated,

 

Hmm at first when you said it only worked on high I immediatly thought well you got a bad resitor pack in the blower circuitry but I almost positive the blower motor is controlled differently.

Since you said other lights were on in the dash that would lead me to beleive that you may have a bad BCM(body control module). It's hard to say without a wiring schematic in front of me or looking at the car.

If wiring/electrical problems scare you as much as me then I think you best bet is going to be to have a GM dealership look at it. I would stay away from small run of the mill shops and stick with a GM dealership since it sounds like a pretty indepth electrical problem.

It probly wouldn't be too hard for a GM tech to figure out cause he could use the tech. 2 to see if he could communicate with the BCM and command the a/c to operate at different speeds and etc.