I have read alot of posts about the blower resistor I changed it but wont work jumped the fan motor it blows but doesnt seem to move with the selector is that a vacuum system ? I cant get air anywhere but defrost vent has anyone run up on this yet I can tell they had it off to replace the radio but dont know anything about the selector area to know its wrong it is a 90 f150 4x4 thanks to anyone that can help