I have a 2005 Tahoe z71. When the AC is on, the

Sounds as if you have more than one problem. If the rear is blowing hot then the AC is not working. The front should also blow hot if the front fan motor is functioning.Youi need to have the system pressures tested for proper freon levels and have the front blower motor system tested if it is not working

Can you hear the front ac/heater fan? They use the same AC compressor so that should be okay. The fan switches fail quite often on those. That controls how much air is pushed by the fan for AC, heat and defrost. The switch is attached to the fan knob on the dash.

CHECK IF BLOWER FAN IS WORKING

Usually a sign one of the blend doors under the dash is stuck or not working correctly.

I think your problem is the head unit that selects where the air comes out ie. Face, floor, defrost, or hi-level face and floor. If that's not working then it will not let you switch location that you want the air to come out.

Just got an answer from Chevy Dealer. When you replaced the battery it loses its memory as to where the door actuators were (the flaps that control the heat and A/C).

The fix:
Turn everything off and let the car sit overnight. The computer should reset itself during its learnings process.
In the morning turn on the ignition and let the car run for a few minutes before turning on the climate control.

If this doesn't work, plan on 1-1.5hours of labor for a technician to reset the actuators at the dealership.

Good luck.


Car Headlights.

A new blower motor resistor

The air bag module or the inflatable restraint sensing and diagnostic module (SDM) as they call it is under the left front seat.

Try hitting the air conditioning canister under the hood with a heavy end screw diver a couple of times both side of the canister. If this doesn't work you will need to charge the canister with freon.

Look at the connector at the blower resistor. They melt. Bottom of right side of dash under the black close out panel. GM sells a repair kit for this.