Prelude - Carbureted Engine
- Remove connector and vacuum hose No. 2 from control unit. Connect vacuum pump/gauge to hose. Using an ohmmeter, measure continuity between Black/Yellow and Brown/White wire terminals on connector. There should be continuity.
- Slowly apply vacuum while observing ohmmeter scale. When vacuum increases above 3.9 in. Hg, switch should open and ohmmeter should show no continuity (infinite resistance). If not, replace vacuum switch A.