My son's 2005 Jeep Grand Cherokee fan control switch is not operating correctly. The switch used to be tempermental with just cutting on and off (not having the multiple blower speeds working) and then he had to jiggle it to get it to cut on or off. I would think that just the blower switch needs to be replaced but I am only seeing where I have to buy the whole HVAC Control Unit. Is it possible just to buy an aftermarket switch to fit into the existing HVAC Control Unit? Thanks.