How to determine proper fuse and wire size?

[795.0]

Does anyone have a link or chart that shows how many amps a given wire size can handle and how to determine proper fuse size?


I'm finally getting around to doing the 3g alternator swap with one rated at 160 amps. (tested at 177 amps max) from alterstart.com. Most articles/posts I've read deal with the 130 amp unit and use 4ga cable and fuses rated anywhere from 125 to 200 amps.
I saw one post that metioned 4ga cable was only good for 136 amps, yet alterstart sent a 4ga cable with this 177amp alt. I'll probably step up to 2ga cable for peace of mind.
Also, they specifically say in the directions, and told me over the phone, not to use any type of circuit breaker or fusible link between the alternator and battery. They also state doing so will void the warranty. I don't understand that and will probably run a fuse anyway, I just need to determine the proper size. Thanks.

 

[jrichker]

Always use a fuse or fuseable link, or circuit breaker in any circuit. No exceptions.
Ford put a fuseable link because it was cheaper than a fuse (no fuse holder).

If the alternator develops an internal short to ground, and there is no circuit protection, you will have an electrical fire.
That electrical fire can burn up your car to a point that it is scap headed for the junkyard.

I would write anyone that sold me an alternator and told me not to use a fuse and ask if the are prepared
to pay the lawsuit and damages from a failure of their alternator.

 

[HISSIN50]

You won't find better advice than that above.


On the cable rating, my take: Some felt it was ok to reuse the stock charge wires in parallel with the new large gauge charge cable (we all know this is a bad idea). The rating of a 4 gauge cable and the additional load-bearing ability (on paper) of the stock wires allowed one to accomodate a larger than 130 amp alternator. Since we're not down with this practice, one needs to use one charge cable that's large enough to accomodate the entire alternator load by itself.

Good luck.

 

[795.0]

Thanks jrichker,
According to that chart I'll definitly go with 2ga wire.
Any idea on how to determine proper fuse size? I've heard it's a certain percentage of max amps, then I've heard it's slightly above max amps.
Thanks.

 

[jrichker]

I would use a 160 amp fuse or somewhere in that range. Fuses will carry up to125% of their rating for an extended period of time without blowing.