My sighing 240

Probably a vacuum leak is letting the vent solenoids relax, it's not the end of the world, but it will probably get worse over time.

That makes sense. Thanks!

There a vacuum hose from the manifold to the firewall that supplies vacuum to the reservoir that sits on the floor under the center console to power the push button vent switches. The nipple at the manifold is too big for the hose, so there is a reducer that uses a small piece of pipe to make a 90 degree fitting. The vacuum hose that fits over the pipe splits and drops vacuum to the reservoir. When the motor is shut off, you hear the air rushing in to fill the vacuum in the reservoir.

Bob

Very helpful, thanks. I'll try to track down the leaky vacuum hose under the hood once it stops being cold and rainy.