Does anybody know how to test this switch? It appears to have both electrical and mechanical components.

I have a Multi-Meter I can use. Any assistance is appreciated. E

 

The switch uses both a solenoid controlled valve and a thermally controlled valve. You can apply 12V to the solenoid terminals and see if the vacuum ports switch correctly. Testing the thermal part is more difficult since the valve is designed to switch as the coolant nears overheating, which is higher than 212 deg with a 15 psi radiator cap. Your Chassis Service Manual will show you which ports do what.

 

I think it goes like this
D- distributor
MT - manifold tap [full vacuum]
C - Carb [ported vacuum]

unconnected at room temp, D should connect to nothing.
Apply 12V across the 2 terminals, click, now D passes air thru C

Heat the TVS [Themal Vacuum Switch] sensor bulb above 240'F or so- hot oil perhaps on the stove? then D is connected to MT. The full vacuum to the dist'r then bumps timing up which alleviates heating issues inherent to retarded timing and also the fan spins faster due to slightly increased engine speed. Water pump goes faster too.

 

Excellent guys. Thanks for the responses. E