GMC Repair: A/C problems, gmc z71, battery terminals

Question
Hi, I recently bought a 2001 GMC Z71. Air conditioner worked at all speeds. Heater never blew hot air. Now the air conditioner only works on 5 speed and temperature setting seems not to work. Any ideas? Thanks.

Answer
Hi
The blower speed is PROBABALLY the blower resistor.
The temperature is PROBABALLY the temp door actuator.
If it is a single mode system (not dual mode) it is located on the drivers side located on the HVAC case.
You MAY try unplugging BOTH battery terminals.
Touch both together for about a minute. Then hreattach the POSITIVE first, then the negative.
I Hope this helps
PAwl