2003 escalade rear a/c unit only blows out hot air, i try to change the control module but they was no power?

there is a diagnostic trouble code set in the auxillary heater ventalation a/c control module. find out what the code is, for example, BXXXX where the x is the number 0-9. this code will, unfortunately, have to be scanned at a dealership. i haven't seen an autozone in my life that will retrieve HVAC codes! the code is probably set for the auxillary temp door actuator control, or paraphrased like that. more than likely you have a bad temperature door actuator. this is located in the rear of the vehicle, near the rear hvac case. i would seek professional help if i was you.