Pontiac Repair: Heater and AC, blower motor resistor, blown fuses

Question
My name is Samone.  I have a 1998 Grand Prix GT.  My heater and AC will not work on number 1 thru 4 but it will work on number 5 (at a high speed).  Now i thought it was the motor blower resister that needed to be changed out but when we did that, it still doesn't work.  What could be the problem?  Is there anyway you can tell me what's wrong with my heater and AC.  Oh also my rear defrost don't work either.

Answer
Hey Samone:

The blower motor resistor is usually what goes wrong with them. If you replaced that and it still is in op. I would make sure that you have no blown fuses for the HVAC head and that none of the connectors are melted either at the back of the HVAC control head or at the resistor. You may have an internal issue with the control head. You should have power on each wire at the resistor for speeds 1-4 power on one wire at a time for each speed and a constant power feed as well it feed the relay inside the resistor assembly. that is if it has manual HAVC if this has the auotmatic system than it's a whole different ball game al together. Good luck :)