Vacuum Switching Valve (VSV)

Connect VSV terminals to a 12-volt power source. See Fig 1. Blow air into pipe A and check that air comes out of pipe B. Disconnect power source and blow air into pipe A and check that air comes out of filter.
Using a volt/ohmmeter, check that there is no continuity between terminals and body of VSV.
Using a volt/ohmmeter, measure resistance between terminals. Resistance should be 36-42 ohms at 68°F (20°C). If resistance is not within specification, replace VSV. See Fig 2.

Fig 1: Testing VSV Valve

Fig 2: Checking VSV Resistance