'87-89 4.9L Injector Blower
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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 (above 170°F). The injector blower relay will disable the motor if the temperature switch goes open (below 170°F) 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.

Unnecessary dead weight; the motor is prone to rust & seize, and the control relay/timer module (usually mounted on the passenger side behind the fan shroud) is prone to overheat. Either can cause a fire, so the system should be disabled & deleted. That's what Ford did around '90.

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Y/LB - hot at all times via Fuse 16
Gy/Y - hot in RUN

Owner caption November 2011 · Photo 3955 of 5000