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Problem:
I have some voltage drop between the battery positive and the alternator. I'm planning to solve it by replacing the wire. I would like to build my own cable and upsize the wire for future accessories. I didn't find any shorts when inspecting the wire.

Questions:

  1. Should I use fusible link or fuses?
  2. If I use a fuse, how do I size it? Its currently a fusible link, I don't see anything in the manual about what size fuses are required for those circuits. I could approximate with a wire guage chart, but I'd rather not make any assumptions.
  3. If I use fusible link, is my math correct here: The B+ to Alternator circuit needs 10GA fusible link.

Background:
The OEM used fusible links, but if I understand correctly the industry has moved to fuses over fusible links.
The service manual says the fusible links should be 4 wire sizes smaller than the wire it protects. It seems fairly straight forward what size and length of fusible link is needed.

Current Wiring:
B+ to Alternator: 6GA (listed as 13mm² in the service manual)
B+ to Underhood Fuse Box: 4GA (listed as 19mm² in the service manual)

Vehicle Info:
1998 Chevy K1500 4.3L v6 262 This is what the service manual says about fusible links Wire Sizing

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  • My understanding of automotive power wiring is that main battery cables are not fusible link wires. They're plain cables sized for the electrical system and can be replaced with larger gauge without issues. You may be confusing the one place where a fusible link wire is used; a separate battery red cable to the alternator. Virtually all vehicles with alternators use a length of specified wire gauge between battery and alternator to prevent internal short circuiting from damaging the battery. Service manual wiring diagrams show and describe fusible link wires.
    – F Dryer
    Aug 10, 2023 at 18:50
  • @FDryer to clarify, the entire length is not a fusible link. There are fusible link segments that are connected to normal GXL automotive wire. These appx 9" segments are closest to the battery before transitioning to normal wire. Fusible link segments are shown in the service manual, and all the OEM and aftermarket parts have them. They're there when I open the hood: i.imgur.com/XcZ2O2D.png
    – ak_
    Aug 10, 2023 at 19:19
  • How would you explain a fusible link wired inline to the main fuse panel? This premise seems questionable since fuse panels are designed to open their fused line when current exceeds the fuse rating. There's no need for a fusible link feeding main 12v power to the fuse panel. A look at any positive or negative battery cable implies all power flows thru large gauge wires, unrestricted. The alternator needs a fusible link wire to protect the battery against a dead short. I don't know if other factory circuits uses fusible link wires. A service manual gives this information.
    – F Dryer
    Aug 10, 2023 at 21:42
  • @FDryer you're right. Its abnormal. As noted in the service manual, that setup is part of the police package that supports additional accessories. I've edited the question for clarity.
    – ak_
    Aug 10, 2023 at 21:55
  • Thank you for the heads up! I didn't know until you mentioned police package and additional wiring to protect added circuits.
    – F Dryer
    Aug 10, 2023 at 22:01

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