New alternator install

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WFarm

Full Access Member
Joined
Jan 11, 2023
Posts
382
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2,353
Location
Central Virginia
First Name
Paul
Truck Year
1975
Truck Model
K5 Blazer
Engine Size
454
I’m planning to install a higher output alternator to keep up with the electric fuel pump and dual electric fan radiator in my 75 Blazer. I’ve studied my schematics and read numerous threads here regarding upgrading charge wire size and wanted to run this by the group before I start.

The new alternator would be a 140 amp unit from Summit (SUM-810344). The current wiring is stock 3-wire, which I want to maintain. In this scheme the charge wire from the alternator runs from the alternator Bat connection to a junction block on the firewall, then a separate wire runs to the starter where it charges the battery via the positive battery cable connection at the starter.

I saw a post from @Ricko1966 that recommended simply adding a separate charge wire from the alternator directly to the battery and leaving the existing wiring intact so you end up with a redundant circuit. Made great sense and my plan is:

1) Install new alternator, adding an additional connection at the BAT terminal that will run directly to the battery + terminal. The current wire that runs from the alternator BAT terminal to the junction block will be connected also as a redundant circuit.

The wire I’ll use for the new circuit is 4awg which is overkill but I have a more than enough of in the shop so why not.
 

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