2-Speed Cooling Fan Motor Circuit (with illuminated switch) only allows the fan to run when the engine is running (because it's powered by the fuel pump relay), but gives the driver control (OFF) for water crossings or (ON) in case the temperature switches fail. In this configuration, speed is always determined by the hi-temp switch & speed relay.
The LED could be inside the switch if polarity permits, or an incandescent could be used ONLY IF the bulb's current draw is less than 1/10 of the fan relay's coil. With this configuration, it will only light if the fan relay is OFF (whether the dash switch is OFF or AUTO). It will only go out if the dash switch is in ON, or AUTO while the low-temperature switch is closed (above 170°F).
For other configurations, see:
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For carb, splice the 3A fuse into any RUN circuit, like the ignition module or voltage regulator.
See also:
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https://www.fleet.ford.com/truckbbas/non-html/1997/c37_39_p.pdfThis diagram was created from this set of symbols using MSPaint:
