Vacuum Switch

Run engine at idle. Check voltage at Green terminal of vacuum switch connector. Voltmeter should read below 1.5V. Disconnect and plug vacuum sensing tube from vacuum switch. Voltmeter should read battery voltage. See Fig 2 .

Fig 1: Idle-Up System (With A/C & P/S)

Fig 2: Idle-Up System (With A/C)
The vacuum switch may be tested off the vehicle. Connect a vacuum pump and a circuit tester to switch. At atmospheric pressure, there should be no continuity between switch terminals. Switch should show continuity at 2.36 in. Hg or below.