Chevrolet Repair: Heater/AC Controls, vacuum line, ac controls

Question
I have a '99 Astro. The heater/AC control is "stuck" on defrost. You can turn the switch but nothing happens.  Also, the fan speed work at low, med & high but shuts off at max.  I have replaced the A/C & Heater Control Switch.

Answer
Hi Jeff, there is a vacuum line that is made of plastic that runs under the throttle body and up to the A/C dryer. You will find that this line has a hole in it near the trottle body. Repair it with rubber hose and then the air flow will change. The blower high speed is controlled with a relay near the blower motor. This relay might be bad or there isn't power to the large red wire going to it.


      Let me know what you find         Mark