I have a 1980 300SD and have located a vacuum leak in the A/C vacuum system. The leak appears to be coming from an actuator which is on top of the unit under the dash. It appears to be the actuator which controls the center duct. My question regarding this is how does one replace this actuator and is this actuator actually replaceable? I am contemplating removing the two ducts which go to the top of the dash for defrosting the windshield but this seems more complicated than it should. I am wondering if there is an easier way. Thanks.