air conditioner only work on high on 2002 Dodge Grand Caravan

hello can anyone help me please!! change already three times the ac relay and keep doing in it!!

Asked by for the 2002 Dodge Grand Caravan
The blower motor resistor is bad ($13 at any autoparts store). The resistor is located under the pass side dash panel near the floor and has a bunch of wires leading into a removable unit. There are 2 screws that have to be removed, pull the thing out, unplug and replace with the new unit. Takes 5 minutes tops. Need a hex socket (#10 ish??) to take screws out.