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As one of the too serious members here I would suggest feeding it right off of the alt w a relay. This keeps tha amperage out of the bulkhead and allows the ammeter to read correct. Want a FL at the alt output stud 2 gauge sizes smaller than that line size.



Running a 30-40 amp circuit off of a 14 ga. wire is a bad idea. Use an ice cube relay like said above. You will need a 12V source that turns on with the key to activate the relay. This would be an acceptable use of the blue wire going to the ballast. For the main power feed to the fan run a 10 ga. wire from the main post on the starter solenoid, alternator, or positive battery post. Also employ a fusible link between the main power source and the relay. It would not be a bad idea to put a blade type fuse holder in line with the switch that activates the relay.