Own a 780 for any time, and you will find that the climate control system often fails to send air where you want it. You are driving down the road on a hot day with the cold air blowing out the dash vents. You step on the gas to pass a car, and the air stops flowing, even though you can hear the blower motor spinning at the same speed.
One of the vacuum bellows that opens and closes the diverter flaps lost pressure and opened (or closed) in the wrong direction. Many manufacturers in the 1980s used vacuum lines to control bellows-like one finds in the 780. After years the rubber gaskets around the bellows dry out and the vacuum pressure is lost. To repair, one has to disassemble the lower dash, which is a labor-intensive project.
The good news for the Concept 780 restoration project is that it is already torn apart and made for a relatively easy restoration. The team went through each of the four bellows testing and replacing as needed. Each bellow was put under pressure using a hand vacuum tool. All of the bellows would have been changed out but they are no longer available. We did find two on Ebay! One more fix taken care of by the Rebuilding Generations team!