Vacuum and More Vacuum

1996 Sonoma Diagrams (for the most part)

In my research before tackling this project, I found quite a bit of useful information, some of it relevant to my 1996 Sonoma and some more applicable to later models. One of the better sources of info came from a discussion at

Below: Similar diagram as my 1996 Sonoma, except for the vacuum line going to the cruise control module. The 1996 Sonoma cruise control module does not use vacuum.

Below: This view is looking into the hose connector that slides over the 3 prongs of the switch.

Above is a schematic showing the actuators and vacuum lines behind the dash.

Above: This shows how the various doors inside the dash work when vacuum is applied to the actuators.

Above: This diagram illustrates vacuum actuators inside the dash, showing which ports get vacuum when the HVAC control knob is in its various settings.

More Diagrams - 1998 and Newer

Above: This is a diagram of later versions of the vacuum actuators behind the dash. My 1996 Sonoma has only 3 actuators. I believe the heater slave valve actuator was added later.

Below: HVAC schematic from 1998 and newer S-series vehicles.

Above: Here's another slightly different version of the 1998 and newer HVAC diagram. This one is helpful because it tells you which actuators should be receiving vacuum under the various settings.