Topic: High-Amp Alternator Cable Upgrade

[Jeffy]

Since this came up on a different thread I through I'd start a new thread just for it.

Here's the gist;  When upgrading to a higher amperage alternator, you want to upgrade the wiring as well.  Stock wiring isn't designed to pass high amperage.

On a YJ, this is 100A or actually two parallel 50A circuits between the Battery and the Alternator.  F2 & F6 in the PDC make up the charging circuit.  The Battery has two leads coming off the +12V.  The 6 gauge red goes to the PDC.  (The 4 gauge loops into the harness and to the starter motor.)  8 Gauge off the Alternator splits into two 10 gauge wires inside the PDC and go to the two fuses F2 and F6.

A TJ is a little different.  It had two 6 gauge wires from the Battery.  One goes to the Starter and the other goes to the PDC.  The Alternator also goes to the PDC but to the +12v terminal that the battery connects to.  Unlike the YJ, the TJ seems to have no fuses but rather a fusible link.  This is basically a fuse built into a wire.  The wire is designed to break under high-amps and not catch on fire, they will spark though.  The advantage is that fusible links are slow blow so they can handle quick bursts of over-amping.  The rule of thumb is 4 gauges lower (add 4) to the wiring.  So on the TJ, with 6 gauge +4 would be 10 gauge which is what they are using.

Here's the breakdown of the amp ratings for a few gauges.

• 10 Gauge = 55A
• 8 Gauge = 73A
• 6 Gauge = 101A
• 4 Gauge = 135A
• 2 Gauge = 181A
• 1 Gauge = 211A
• 0 Gauge = 245A

There are two choices you have when adding a path from the alternator.  One is to bypass the PDC all together.  You will need a large fuse or fusible link to handle/protect the charging circuit.  Keep in mind, you will still have three wires off the battery terminal as you still need to power the PDC and power to the starter as well so you can't really clean it up much there.  The other option is to run another line from the alternator directly to the battery.  If you want to double the load capacity then use 6 gauge to get combined 202a circuit.  Or go larger to give yourself some additional overhead.

[fatoldcapt]

Stupid is as Stupid Does.... This info was of some use to me as I bought and installed a 200 Amp alternator with no thought of any other issues. But just to save me from getting out the shop manual, what's PDC, PSD, F6 & F2 ?

I'm a simple sole and need as much help as I can get to understand this stuff. (So I don't burn it all up) Remember the earth is flat and electricity is magic.
Thanks! Aaron

[sharpxmen]

Stupid is as Stupid Does.... This info was of some use to me as I bought and installed a 200 Amp alternator with no thought of any other issues. But just to save me from getting out the shop manual, what's PDC, PSD, F6 & F2 ?

I'm a simple sole and need as much help as I can get to understand this stuff. (So I don't burn it all up) Remember the earth is flat and electricity is magic.
Thanks! Aaron

PDC = power distribution center (it is located by the battery on the fender well in the engine compartment). PSD i think it's a typo and refers to PDC

F2 and F6 are the 2 x 50 amp fuses for the alternator located in the PDC

[Jeffy]

I'll see about getting some pictures to help explain it all as well.

Yeah PSD was a typo.

[fatoldcapt]

Thanks! That answers all my questions. I know where all that is and can make adjustments as you suggest.
Aaron

[Bounty Hunter]

I just added an additional heavy gauge cable from the alternator to the battery after installing my hi-amp alternator.  Should the ground be upgraded as well?

[Jeffy]

I just added an additional heavy gauge cable from the alternator to the battery after installing my hi-amp alternator.  Should the ground be upgraded as well?

It shouldn't be necessary.  Current flows in one direction.  High-amps are stored in the battery and don't come back to the alternator.  The YJ uses 6 gauge which is good for 101A.  Just make sure your grounds are good.  If you have a winch, then you'll probably have additional grounds anyway.  Just need to make sure the engine to the chassis ground is OK as well as the block to battery.

[TheNewbie]

Good info.  I just did the 136 amp alternator mod and will be doing the wiring to match before I add any additional load.

I wasn't aware that I could just replace the wire from the alternator to the battery thoguh.  I thought I had to do them all.

[czjeeper]

This is what I did.

I've got a wire going from the alternator (136amp) to a 150 amp fuse on the firewall, then to the battery.
The PDC is bypassed, and it powered by a wire directly to the battery.
Other wires in this mess are the starter lead, and my winch lead.