I am having the same problems. Changed the blower resistor and nothing changed. Fuses are all ok and I know that it must be the vacuum. We are all looking for a solution; please help us FastCougar owners and contributors.
Ok solved mine. It was a rubbed/abbraded/burnt/melted vaccum line in the engine compartment that passes through the firewall. It is a grey line connected to a black line ( the black line passes the firewall)
Diagnosis: Removed glove box and then removed vacuum line comming in from engine ( see photo), placing thumb over end (with engine running) felt no vacuum, the let me know that it was in the engine compartment.
In the engine compartment- I traced the vacuum lines, the grey line ( center line on engine, on top, near firewall) comes off a "T" and provides the vacuum for the vacuum actuators in the cabin that move from defrost to other positions. . Upon inspection with a flashlight, I could see a darkened spot on the line about 4-5 inches down from the junction, that appeared to be melted, leaking etc.
Remedy: I cut the piece off, went to AutoZone, got some 1/8 " HVAC tubing and some conectors. I used that to patch the line. ( Word of caution, there was virtually no slack in the line, where you cut is where you will be mending, not a lot of space behind engine to force on a connector)
Result: Everything works fine, I can switch from defrost to panel and it works.
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