1997 Tahoe,Blower motor only blowing on low.Changed the blower motor & still have the same problem.Is it the heater control being bad?Do these go bad? Thanks in advance Dave

Two things , could be the blower resistor located near the blower motor, it has several wires going to ii and then to the blower, if not it is probably the switch

Well first you needed to check a blower resistor block, this regulates amount of voltage controling motor speed, this block is usually located close to bloer motor follow your wires to it, remove two 7mm screws an check, if is all rusty just replace it, if not back prove to make sure controller is sending signal to each speed, (test lite hook to a power sourse) you been looking for a ground signal. hope it helps and good luck

Gain room by pressing on right side of open glovebox. it should come off its hinges. just set it aside. you can see the HVAC box. Look on top of the HVAC box and a little to the left and you will see the blower motor resistor mounted snuggly. have a good day !