E 350 Van L6-300 4.9L VIN E 1-bbl (1982)
Thermal Vacuum Valve: Description and Operation
This system used on some vehicles, consists of an ambient temperature switch, a three-way vacuum valve, a latching relay and an external inline
vacuum bleed. The three-way vacuum valve is used to select the carburetor vacuum source that is supplied to the distributor vacuum advance
mechanism. The ambient temperature switch provides the switching circuit to determine which vacuum source will be selected as a function of outside
air temperature. The latching relay, activated by temperature switch closing, remains energized regardless of temperature switch position which prevents
system cycling due to minor ambient temperature changes. The inline vacuum bleed function is to purge the vacuum line in the CTAV system of any
excessive gasoline vapors.
