Vacuum Switch: Testing and Inspection

1. Check vacuum switch A as follows:
a. Remove control box from firewall, then remove cover from control box.
b. Disconnect hose No. 2 from vacuum switch A and connect vacuum pump to switch.
c. Attach positive probe of voltmeter to No. 1 green/yellow terminal and negative probe to No. 32 black terminal of control unit connector.
d. Turn ignition switch to On position and check for voltage. There should be no voltage when vacuum above 3.1 inches Hg is applied and there should be voltage when vacuum is released.
2. Check vacuum switch B as follows:
a. Remove control box from firewall, then remove cover from control box.
b. Disconnect No. 7 vacuum hose from vacuum switch B and connect vacuum pump to switch.
c. Attach positive probe of voltmeter to No. 8 yellow/blue terminal and negative probe to No. 32 black terminal of control unit connector.
d. Turn ignition switch to On position and check for voltage. There should be no voltage when vacuum above 1.2 inches Hg is applied and voltage should be available when vacuum is released.
3. Check vacuum switch C as follows:
a. Remove control box from firewall, then remove cover from control box.
b. Disconnect No. 7 vacuum hose from vacuum switch C and connect vacuum pump to switch.
c. Attach positive probe of voltmeter to No. 2 yellow/red terminal and negative probe to No. 32 black terminal of control unit connector.
d. Turn ignition switch to On position and check for voltage. There should be no voltage when vacuum above 2.4 inches Hg is applied and voltage should be available when vacuum is released.