Component Testing
- If air pump clutch operated with engine at idle and normal operating temperature, check coolant temperature switch with volt/ohmmeter. If zero resistance is shown, replace switch. If infinite resistance is shown, replace relay.
- Coolant must be about 212°F (100°C). With engine idling, disconnect oxygen sensor and coolant temperature switch. Connect a jumper wire across coolant switch connector terminals.
- Clutch should operate. If not, check for voltage at temperature switch connector. Repair wiring as necessary.
- Reconnect temperature switch. With oxygen sensor still disconnected, remove vacuum line from air shutoff valve and connect a vacuum gauge to line. No vacuum should be present. If vacuum is noted, unplug temperature switch connector.
- If vacuum drops, replace coolant temperature switch. If vacuum does not drop, repair or replace wiring, relay or switchover valve.
- Connect a jumper wire across temperature switch connector terminals. Vacuum should be present on gauge. If not, check and repair vacuum lines as necessary. Check shutoff valve for leaks.
- Pull hose from air cleaner leading to air pump. If strong suction is present, system testing is complete. If no air is drawn in, check hose condition or replace air pump. If a slight amount of air is drawn in, pull Purple/Blue vacuum line from air switchover valve. If vacuum is present at valve, replace it.