In my 94 burban, when i turn the key on for the first time, and also once i turn the key off, there is an annoying clicking noise. I know its one of those lil electric motor thingys for the blend. it's an a/c truck so there's 3 and they're a bear to get to. all I'm able to find them from is the dealer, any aftermarket place make them? or is it dealer only?