Ported Vacuum Switches & Vacuum Control Valves

Fig. 22 Ported vacuum switches & vacuum control valves:

Fig. 23 Electrical vacuum switch:

VACUUM SWITCH TEST
1. With engine cold, turn ignition key to ``ON,'' connect vacuum gauge to port A, Figs. 22 and 23, and a vacuum source to port B and then C. There should be no vacuum flow from A to B but there should be vacuum from A to C.
2. Start engine and run until it reaches normal operating temperature, then apply vacuum to port B and then port C. There should be vacuum from A to B but no vacuum from A to C. On 4-port valve, check A1 to B1 and A2 to B2 separately.
3. If vacuum flow is not as described, replace valve.




ELECTRICAL SWITCH TEST
1. Using a suitable ohmmeter, measure resistance across switch terminals with engine cold and note reading.
2. Start engine and allow to reach operating temperature, then measure resistance across switch terminals.
3. A change in resistance should be noted at cold and warm engine temperature readings.
4. Check vacuum portion of switch as described above.