Jeep Repair: jeep a/c repair, blower motor resistor, diagnostic routine

Question
my girlfriend's jeep liberty 2002 a/c and heater do not work on the low settings 1 and 2 but do work on the high settings 3 and 4. how do i go about checking what the problem might be?

Answer
Although I could lead you down the whole blower motor diagnostic routine, it would be just a waste of time. The problem with your girlfriends Liberty is one we see often. You'll need to replace the blower motor resistor. It's located near the blower motor on the passenger side of the dash. Two screws hold it in place and it is easy to replace,