Alternator Wiring Question

[alice]

I have my OEM 96-98 Galant alternator on my 2g wired stock to the fusebox through the stock alternator fuse then to a 200amp ANL fuse to 4ga wire to 140amp circuit breaker then to the battery which is in the trunk. Tonight, while out on a cruise, I started tripping the circuit breaker every few minutes obviously cutting power to the battery and its got me thinking.....If I'm tripping the 140amp circuit breaker and not blowing the stock 100amp alternator fuse, wouldn't this suggest that the circuit breaker is a faulty unit because its tripping before the fuse is blowing?

I believe the Galant alternator is like 96amps or something like that so why would I be popping the CB first and not the fuse?

 

[wrencher]

The circuit breaker is a thermal bi-metallic switch.
It can be stressed & reduce it's rating.
Thermal cycling of a breaker degrades it.

That comes to how this breaker is installed.
Out of the stock underhood box, you have a fuse & then the breaker?
The starter wired of this circuit as well?
Trying to picture how many connections you have in this circuit @ the fuse box.

Connections plus the run of 4 gauge to the trunk will create resistance.
Resistance even in tiny amounts is a load to a circuit.
The connections are real important here due to the nature or this circuit.
That can heat the breaker, stressing it constantly causing it to trip.
Then as it keeps heating & tripping it will degrade it's capability.


There are some other issues using circuit breakers, they have to be matched to the circuit to operated properly.
Not just the installation/connections are important.

The circuit breaker rating that matches the wire size the breaker is trying to protect. If the wire size is too small or too big for the breaker, the heat sink characteristics of the wire will shift the calibration curve of the breaker up or down, respectively.

If the wire is too big, the breaker will respond more slowly to a current overload, thus inadequately protecting the wire.
If the wire is too small, the breaker will open earlier than designed, potentially causing electrical system malfunctions.

 

[alice]

Here's a semi visual of how my alternator setup goes:

[Alternator (4 White Wires)]-->[Fusebox through stock 100AMP fuse]-->[white wires that originally connected directly to the battery]-->[200AMP ANL Fuse]-->4ga wire to the trunk to [140AMP Circuit Breaker]-->4ga wire to battery

So, I am tripping the 140 AMP circuit breaker which is about 12" from the battery but not blowing the 100AMP fuse in the fuse box. Wouldn't this suggest that either the circuit breaker is faulty or there is a flaw in the alternator system in general?

 

[wrencher]

So you have the starter wired in where in there?
If the 4 ga is feeding the starter, a 140 CB is gonna get stressed.
That & IMO way too small for 12-14 foot run of cable for 140 amps.
Which the starter will likely draw more amperage than that & with those numbers your well over a half a volt in voltage drop using it for the starter.

12 foot 4ga approx 10 volts cranking 140 amp load= .83 voltage drop. Too high...
And like I said the amperage is likely higher than that which makes the volt drop much worse.
All the exact numbers are highly subjective per vehicle, but 4 gauge being a constant it never comes out good.
I would put another 200 amp fuse in there @ the battery to replace the CB at the least.