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Thermal Vacuum Switch (TVS)

  1. Remove TVS from air cleaner. Attach small, center nipple to a 24 x 1/4" piece of vacuum tubing which is connected to an external vacuum source. Leave other nipple unattached.
  2. Obtain a can of R-12 refrigerant, a safety valve and a suitable piece of refrigerant hose. With safety valve closed, attach R-12 can to valve and hose to valve.
    CAUTION: Wear eye protection and make sure area is well-ventilated. When working with R-12, make sure engine Is NOT running.
  3. Invert R-12 refrigerant can, slowly open can valve, and apply liquid refrigerant to TVS to cool it to 40°F (4°C) or less. Apply 16 in. Hg with external vacuum source and hold. Vacuum level must remain at 10-16 in. Hg for 60 seconds. If not, replace TVS.
    Fig 1: Testing Thermal Vacuum Switch
    G09313215Courtesy of FORD MOTOR CO.