I have a 2004 chevy trailblazer. Car was stalling at light when I had the ac on. I cleaned out the throttle body. Everything was fine. Now the ac doesn't blow out of the top vents to your face. What should I be looking for to fix this problem?

You probably unhooked the battery recently if this just started. Classic dirty throttle body syndrome. Unhook the battery, yank the throttle body off (only 4 bolts) and clean with a product like a sensor safe Seafoam and a rag, do not use wire brush or something abrasive, will damage the aluminum. Can re-use the hard plastic O-ring many times over. Hook the battery back up and drive around for 15 minutes or so. This is THE most popular problem with Envoys and Trailblazers. After the original battery was unhooked, the computer thought the throttle body was clean, which it is not, so you will have idle problems when the A/C or Defrost is on. Before you unhook the battery for cleaning, make sure you turn OFF all HVAC including AC or Defrost, or you the vent actuators can go bad on you.

Certainly sounds like the ac compressor is stalling the vehicle. This usually occurs when the high pressure switch in the system is faulty, and not deactivating the clutch temporarily when it senses a high pressure in the system. An intermittent failure in the switch is not uncommon - try having it replaced.

Many of the 6 cyl. engines are prone to carbon build-up in the throttle body. If this is the case, it is best to clean it off the car and is fairly easy to do. Remove the snorkel, 1 electric fitting on the throttle body (a little tricky) and one vacuum line on tb as well. Four bolts remove the tb from the engine and the throttle body can be cleaned with throttle body cleaner from any auto supply store. An o-ring attaches the tb to the engine so that you will not destroy a gasket during the repair. Pretty easy and should take less than 1 hour, but be careful of sharp edges in the throttle body.

ONe of the "easy" fixes is buy a can of throttle body cleaner. Remove the air intake near throttle boddy and clean the inside of throttle body as best you can this should help it. If it doesnt have it checked out it could be more advanced problem. Good Luck.

For the stalling issue, the throttle body needs to be cleaned, grime in this area prevents the throttle plate from closing completely and allowing air to enter, making the air/fuel mixture lean.
The dead speedometer could be a bad stepper motor in the instrument cluster or a bad speed sensor on the transmission. If the cruise control is not working, the problem is most likely the speed sensor.

The throttle body needs cleaning, grime and debris has built up on the throttle plate and surrounding area preventing throttle plate from closing completely at idle.

remove the airduct work at the throttle body and clean the throttle body good and the problem will be gone

The throttle body needs to be cleaned, grime build up in the throttle body and throttle plate prevent the plate from closing completely and stalling the car. While cleaning the TB, disconnect the battery for about 30 minutes and set all HVAC controls to off position or fully counterclockwise. After reconnecting battery, do not touch HVAC controls, turn key to ON position but do not start, wait about 10 minutes then start.

Throttle body needs to be cleaned.

clean your throttle body....same thing happened to me and my truck runs great now.