My wife's 1988 S-15 Jimmy has a vacuum leak in the heater/air conditioner control head (behind the levers which control temperature and air flow). Two competent shops AND a not-quite-so-competent dealer have been unable to fix this, because all of the replacement parts have been defective, right out of the box. Can someone suggest where to find a control head which doesn't leak, how to fix a leaking one, or how to find someone (in Colorado or perhaps Nebraska) who truly knows how to fix one?
These control heads are a wonder of vacuum engineering...when they work. Two plastic discs rotate against each other, directing vacuum through an intricate maze of passages, thus moving vacuum-powered actuators which control the air flow. In many cases, one of the plastic discs seems to be ever so slightly warped, thus "letting the vacuum out." :-)
Paul