I have a 90 4x4 22RE and i dont have a cabel going directly to the alternator like explained in this thread. I had a positive going to the starter and to fuse box. Negative going to the block and grounded to the chasis by the fuse box. I think I have that correct. Is this normal?

 

It's thru the wiring harness to the alternator (or actually to the battery from the alternator.

 

I am getting ready to do the big 3 wire upgrade with my new high amp alternator and I have seen the talk about fusing the wire between the alt and battery. I might go with a 200 amp circuit breaker since I have one lying around, but probably not necessary. I went through this on my Early Bronco and the advice from Ray from http://www.svapowerproducts.com/ was the following. The concept is the same even though he is discussing the 3G alternator.

" Fusing an Alternator
Wrote this rather quickly this morning, so it may contain some errors or be adjusted in the future. But you should still be able to understand the gist of what I am trying to explain.

How Big of Fuse?

I am writing this to help determine the size of a fuse to use in the alternator’s main battery output cable, i.e. the cable from the alternator to the battery. To date I have never used a fuse or circuit breaker in this line. But since many would like to use one, I would like to explain what they will and will not protect against.

First using too small of a fuse or circuit breaker can cause many problems. In a 130amp 3G the fuse should be a minimum 160amps, preferable 180 or 200amps. As when the stock alternator is loaded way down, it can produce 160amps at about 12.8 volts. This varies from alternator to alternator and is much higher for high output alternators. Better to be safe than sorry, so using a 200amp breaker will keep the margins or error wider. But does a 200amp breaker offer the same protection as a 130amp breaker. The answer is yes when you consider what it is actually protecting you against. Lets look at possible causes of shorts in the alternator charge circuit.

Regulator Stays On: This causes the field to be continually on. Which puts about 6amps directly through the rotor to ground. This causes great heat, but the battery usually drains to zero before a fire. Regardless it is only 6amps, so neither a 130 or 200amp breaker will open.

Rotor Shorts Internally: This causes a directly positive to ground short. The 24-20gauge brush lead will melt instantly. Kind of acting like a fuse of about 10amps. Then the brush spring will try and carry the load, and melt as well. So neither the 130 or 200 breaker will open.

Diode Shorts: This causes a direct positive to ground short. The diode’s lead is only designed to carry 50amps (stock), 70amps (HD aftermarket). So it will melt almost instantly. So neither the 130 or 200 breaker will open.

Stator Shorts: This causes a heavy positive to negative short. This can cause a fire as all the amperage created by the alternator is going to ground. But the alternator is the source of the power, so the breakers will not be able to prevent this. Once the alternator has fried the stator, it then becomes possible for the power to come from the battery to the stator. But this is only if the diodes have failed by becoming shorted. If so see above.

Main Battery Post Becomes Loose: This can cause a fire, in fact 10,000 or 1000’s of fires happen on Ford products equipped with their 2G alternators, because of this. Since the fire is started by heat in the loose connection, it is the alternator that is producing the power that creates the fire. So breakers and fusible links will not and did not prevent this.

Main Battery Cable Shorts: This causes a direct to ground surge, usually large enough to burn/blow the wire in half instantly. If you are using a 4ga cable, it is possible several hundred amps will go to ground. So either a 160/200/300 amp breaker will open in this situation.

Side Notes: A couple of things you should know. The next gas deliver truck you pull up beside, likely has no fuse between the alternator and batteries. If your breaker pops while the alternator is charging, there is a good chance it will blow the diodes. Sometimes they blow with enough force to send shrapnel through rads, A/C condensers, and people if your hood is up.

In the end a breaker only protects your system from a cable short between it and the alternator. It will not help with most other problems, including a cable short between it and the battery. So going a little bigger with the breaker, if you use one, is actually safer both physically and financially."

 

time to bring back an old thread!

I'm taking my engine out tomorrow, and since i have the room i'm gonna do all the wire upgrades with 4ga..those of you that ran a wire parallel with fuse box and alt was that because it was difficult to access the wire? I would like to just replace the wire all together, but if its more beneficial to have two i'll just leave it and run another..

 

A couple of reasons why I went the parallel route.

First, yes, it is a pain to get the wire out of the fuse box, but, that was not the primary reason, as it is just work, not impossible.

Second, and the main reason I did it, is that the additional current I am pulling for all of my goodies and add on's does not flow through the fuse box and the fusible link. So, I do not really need to upgrade that circuit, as the big fat parallel wire will handle that side for me. My winch is run directly off the battery. My offroad lights, back up lights, horn upgrade, stereo, etc are all run off of a distribution block on the wheel well that is tapped directly to the battery with 4 ga wire.

Link to my high output alternator install with the parallel wire from the alternator:

https://www.yotatech.com/forums/f127...nstall-206450/

 

so...

1. did you fuse the new wire at all? that thread doesnt mention it or no pixs of it.

2. so the OEM wire is piggybacked with the new wire on the alternator post?