i recently had to take out the heater box on my 2000 xj. i had no heat and after replacing the eater core and finding a crap evap i replaced that too. the problem ihave now is that the blower motor does not work ont he 4 position. it works on all temp modes and it works on all levels but 4. i changed the resistor before but when that goes bad i shoudl only have high and nothing below that. any help would be great