Injector Cooling Fan Switch (170 degF) for '87-89 4.9L only
STEMCO 431-5040 F170 89019A
Below 170degreesF, it's open (OFF); above, it's closed (ON). Neither wire is connected to the brass face (NOT grounded), but it can be wired up that way if necessary.
The injector blower motor is powered by the relay for a maximum of 15 minutes when the ignition switch is OFF and the temperature switch is closed. The injector blower relay will disable the motor if the temperature switch goes open (cool) or if the ig.sw. is turned to RUN. Test the relay & motor operation by turning the key OFF and grounding circuit 743 Bk/LB; the motor should run for approximately 15 minutes, and then stop.
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