I pulled out my HVAC controls to look and see if I have the typical vacuum leak issue. It appears to be spinning like it should and doesn’t look broken. Also when I pull the rubber connector off, I don’t hear any “hissing”. Should it hiss when I pull back the rubber piece? Could it be something else, or is this probably the control/mix vacuum switch still?

 

Do you mean that the fan blows but only to the defrost vents? Or does the system only kick on when set to defrost?

For troubleshooting vacuum, grab a cheap hand vacuum pump from Amazon, Harbor freight or wherever. Hook it up to the diaphragm and make sure it holds vacuum and operates. Find the supply line and hook the diaphragm back into the system and apply vacuum to the supply, see if it holds. If not, inspect the hoses and connections to find the leak, replace it and be on your way. All the vacuum hoses in these cars should have been replaced by this point anyways, get a few yards and go to town replacing one at a time until everything is new. You can get connector kits at the auto parts stores or online.

 

If there's no hiss, there's no vacuum.

Trace the vac line that comes through the firewall near the heater hose connections, in the HVAC wiring harness. It's probably disconnected somewhere.