From Don Verity:
Here are pictures of the heater switch that controls the blower motor and the vacuum-operated doors.
The new switches are a little different but can be set up to work just like the original switches.
The alligator clip is on the power supply terminal.
The open terminal next to it goes to the fan switch.
The jumper wire provides power for the compressor clutch wire,
which would connect to the terminal under the jumper.
Some use two power feeds, one for the fan, and one for the compressor clutch.
In the off position there should be no power to any other terminal.
In Max and Fresh A/C there should be power at the clutch wire and the fan terminal.
In heat and defrost there should be only power to the fan.
Some switches supply power to the A/C clutch when in the defrost position.
Click to enlarge