My 99 HE air stopped working book symbol came up on ac display , found drivers side fan no go . found relay burnt out replaced & fan ok & symbol gone cleaned the intake filters . But no air coming out of the vents regardless of what I select though I can hear it change from fresh to recirculated So i suspect servo motor/s are stuffed . ,but how do i test them to see which ones are stuffed . I have a wrecker who has several servos so are they all the same ?