Alternator and wiring upgrade

[Tsoptich83]

I'm having an issue figuring out if when you upgrade the alternator, do you have to upgrade the fusible links and wires from the starter and alternator? If I upgrade from the 78amp alternator to a 100 amp or larger is it acceptable to upgrade the wiring to 4 gauge and replace the fusible link for the alternator to a mega fuse and run 4 gauge cable to the starter with out a fuse at the starter? (That's how it's done with the 3g upgrade in the fords) Correct me if I'm wrong and thanks in advance.

Thomas

[Dead Parrot]

If you have access to a pull-a-part type place, find a main alt wire set from a 90+ GM truck with a CS type alt. Should be sized properly for the size alt you are installing and will include the proper fusible link. Might even get one of the 90s type multi terminal junction blocks.

[hatzie]

The Charge wire is usually 12AWG (3mm²). You can upgrade to 10AWG with a 14AWG fusible link. It's not strictly necessary. 12AWG should actually be fine. You aren't going to be running the alternator full bore for any length of time. It'd overheat. A 105A CS130 gives you a larger buffer between operating amps and full bore than the old 78A 12SI along with better bearings and exponentially better cooling... I've jump started fairly big farm tractors and front end loaders with an old 10SI in an IH Scout 800A with only 65A output.

There are usually two charge wire runs involved.

• Alternator to Junction Stud. 5/16 (8mm) ring terminal on the alternator and 1/4" on the J-Stud.
• 1/4" Junction Stud to 3/8" BAT terminal on starter.

The stock GM main battery cables should already be made of 32mm² (2AWG) copper battery cable. 4AWG would be a downgrade.

[Tsoptich83]

Thanks for the information. It was all a little different to me having come from the Ford side. I have seen a lot of threads or posts about upgraded alternator but nothing about upgrading the wiring or cabling. I am not in the market for the upgrade as of right now, but I have considered upgrading the stereo system, lights and what not. But for now I feel the 78 amp alternator will suffice, since everything is original. I saw a link last night for replacing a fusible link, but I cant find it now. Also I saw some posts that you made hatzie about wire size and such.

I am correct?
1: Cross section (mm2)
2:Wire Color
3:Circuit number

[hatzie]

Originally Posted by Tsoptich83

Thanks for the information. It was all a little different to me having come from the Ford side. I have seen a lot of threads or posts about upgraded alternator but nothing about upgrading the wiring or cabling. I am not in the market for the upgrade as of right now, but I have considered upgrading the stereo system, lights and what not. But for now I feel the 78 amp alternator will suffice, since everything is original. I saw a link last night for replacing a fusible link, but I cant find it now. Also I saw some posts that you made hatzie about wire size and such.

I am correct?
1: Cross section (mm2)
2:Wire Color
3:Circuit number

Correct.

3mm² is 12AWG.

The `83 diagrams don't have the mm² to AWG table and I forgot to add it from one of the other wiring diagrams. Download the 1979 diagrams that have that table on the first page.
Some of the later wiring diagrams don't have the stud sizes at the starter and junction block. You can find that info in the older wiring diagrams. 1973 lists all three starter solenoid studs. 3/8 #10 & #8.

Note the (SXL) at the end. This is the GM specified wire jacket type. Type S Crosslinked-Polyethylene. I use SXL for all automotive repair wiring except battery cables. SXL is available in 8-20AWG.
The GPT PVC jacketed wire available at your local auto parts stores doesn't meet the SAE J1128 spec for heat (125°C), petroleum, chemical, and ozone resistance for automotive wiring.
I use SGX (Starter or Ground Cross-Linked Polyethylene) to build new 0-4AWG battery cables on my machinery... 4AWG is for the batteries on my lawn mower, snowmobile, and ATV. Cheap SGT & SGR battery cables that you usually find stocked by the Borg don't meet SAE J1128.

GPT & SGT jacket is only rated to 85°C. SGR is rated to 90°C.

You can type many useful symbols on a PC using Unicode ALT codes. Google em. The list is nearly endless.
Set the Num-Lock to ON, Hold down an ALT key and type the numbers on your numeric keypad.

• Squared ² (superscript 2) is ALT-0178
• Degrees ° is ALT-248
• Ohms Ω (upper-case Omega) is ALT-234
• Long division symbol (Obelus) ÷ is ALT-0247

[Tsoptich83]

Thanks for the help and info Hatzie. That makes it a lot easier. Lost thing are there any updates or upgrades that you recommend are for as the electronical system is concerned.