Originally Posted by Hotrod_Ford
I'm on the age old topic of ignition wiring. I want to do my F1 Ford truck's wiring in three phases (Ignition, Accesories, Lighting). Attached is the diagram for the ignition wiring.
Ignition: The IGN 12V falls away when I turn the ignition to 'Start'. I was told to add the pink wire to the terminal between the starter and its solenoid to provide direct 12v to the coil when the starter kicks in. Is this ok? There is a 5th pin on the starter 'R' that also gets 12v when the ignition is on 'start' that can be used to provide the 12v but then everything goes through the ignition.
No need to run the pink wire w/diode from the starter you described/illustrated if you have an 'R' terminal on the ignition switch. That's what the 'R' terminal is for; to send full battery voltage to the coil during startup. Run a 14 or 16 gauge wire from the 'R' terminal on the switch to the coil side of the ballast resistor, or the coil + terminal. No need for a diode this way either.
Alternator: The yellow 8 or 10 guage wire goes from the B+ of the alternator to the + on the battery/solenoid. I was told that 30 or 50 amp fuses are too small. Normally on the older alternators you connect the 'charge indicator' to the terminal on the alternator and to the Ignition wire between the ignition and the balast resistor. I have a newer Bosch alternator and I only have a B+ and a 'L' live connector on it. How do I connect the charge indicator and how do I excite the alternator? I indicated the normal connection in the white and black wire.
Could be that I'm just old fashioned, but it is not customary to use a fuse in the alternator output wire. Maybe they do it on late models, I don't know. I use a fuse link
on the alternator wire at the connection to the solenoid. The fuse link should be two sizes smaller than the wire it is protecting - on an 8 gauge wire, use a 12 gauge fuse link. The fuse link should be 4"-6" in length.
If I was to use a fuse on the alternator output wire, I would use one rated for well more than the alternator is rated to put out. Your alternator is probably rated for at least 55 amps. A 50 amp fuse would not be enough. The idea is to protect the wire in the event of a short, not to limit the alternators output. How big of fuse to use? I'd figure out what the output of the alternator is and add 50% or more.
I'm not familiar with your exact alternator, but based on this diagram
I think you're on the right track for wiring it. According to this diagram, you may also need a diode in the charge indicator wire to keep the alternator excitation circuit from backfeeding the ignition coil, which may cause engine run-on when you turn off the ignition switch (I forgot to add this diode in my alterations to your diagram).
Hope this helps....