Prizm L4-1600cc 1.6L DOHC VIN 5 (1989)
Vacuum Check Valve HVAC: Testing and Inspection
Vacuum Switching Valve (VSV) Test
Inspect
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Remove vacuum switching valve from engine compartment.
VSV Testing
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Connect VSV to battery as shown in the illustration.
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Blow air into pipe "A" and check that air comes out of pipe "B" but not out of filter "C."
VSV Testing
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Disconnect battery. Now, blow air into pipe "A" and check that air comes out of filter "C" but does not come out of pipe "B."
Check for Short Circuit
VSV Testing
Using an ohmmeter, check that there is no continuity between either terminal and the VSV body. Continuity would suggest the presence of a short
circuit. Replace VSV if a short circuit is found.
Check for Open Circuit