GMC Repair: 4x4 service light, blower motor resistor, chevy trailblazer

Question
Chevy Trailblazer 2002                 The service 4WD light has come on and stays on. The transfer case control switch only works in two wheel drive position.  The other problem I have is the heater/AC fan will not work on the first two settings,it only works on 3-4&5 positions. Question is what to check or replace?  

Answer
O.k. you have 2 seperate issues,...

1. You blower motor resistor needs to be replaced. That will fix the A/C issue.

2. You have a problem in your 4WD control circuit, and you need to have it diagnosed by a porfessional to see what the problem is. You at least need to find out what trouble code has set to turn on the light. I would advise you to bring it to your local dealer for a hands on diagnosis.