Diesel Forum - TheDieselStop.com - View Single Post - 12v aux wire origination
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post #2 of (permalink) Old 09-13-2018, 02:12 PM
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BBB Industries- Premium Alternators, Starters, Power Steering Products | TSB's & Wiring Diagrams
When you see the "WIRING DIAGRAMS" button, click it before selecting the system. If you can't find the diagram for your year, try a later similar truck.

It doesn't connect to the alternator - it probably originates near the L hood hinge, where the other relays are (originally under a black plastic cover). This is what the trailer relay harness looks like on '87-91 F150s & Broncos (& possibly F250/350s):

(phone app link)

(phone app link)

But the charge wire might come straight from the starter relay as a simple fusible link.

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Last edited by klhansen; 09-14-2018 at 01:08 AM. Reason: forum rule violation
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