Recently I noticed that the "selector switch" (A/C, heater, vent, etc.) on the heater HVAC control panel in a 1989 cavalier didn't move well. It also didn't work (turned the fan on, and nothing came out of the defroster, vents or heater). I pulled the heater control panel, and the vacuum selector switch inside was actually in pieces.
(See picture) Note that the vacuum connector to the switch, as well as the temperature control slide cable, are held by the metal fasteners circled in red in the picture (the picture shows the underside of the heater control assembly). I don't know what these are called, but they are difficult to install and remove. I broke the posts on the vacuum switch trying to remove the vacuum connector, because I didn't know those fasteners were there (irrelevant, because I was replacing that switch anyway), I did see the fastener on the temperature control slide, and carefully worked that one off with a pair of needle nose pliers.
I replaced the vacuum selector switch (part 16037768/15-71032), and instead of using the old fasteners, I used a couple of 1/8" ID (x 11/32" OD) rubber washers/grommets, which slid easily (but fit very snugly) over the vacuum connector mounting posts on the new switch. I used the same grommet on the temperature control cable, but I installed a small metal washer between the rubber washer/grommet and the cable. Actually, I am not even sure if the fasteners for the vacuum connector are even necessary.
Washers/grommets were purchased at an ACE hardware store, but they might be available at other hardware or home improvement stores.
I imagine that other GM cars, particularly of that era, are similar.
- Vacuum switch.jpg (154k)
HVAC Control 2.JPG (239k)