22re wiring help - GM 1 wire alternator swap

Kickdeez

Kickdeez

Well-Known Member
Joined
Apr 6, 2010
Location
Charlotte
89 4runner with the 22re

In addition to cleaning up the under hood wiring a bit, I’m swapping out the factory alternator for a GM 1 wire. Right now, I’m trying to figure out what to do with the wires that are currently hooked up to the “Glow/Am 1” 80A fuse in the fuse box located behind the battery.

Fuse layout:
IMG_9174.jpeg


This is the 80A fuse. It’s shot, and I’m replacing it.
IMG_9159.jpeg


This wire (on the left side of the fuse - it’s white) runs to, what looks like, an in-line fuse/circuit breaker on the driver side inner fender, and then connects to the positive post on the factory alternator. I’m not great at reading wiring schematics, but according to my Haynes manual and my multimeter, that white wire also splices into at least 1 other wire (maybe 2) that runs to the 40A “AM 1” fuse in the same fuse box.
IMG_9160.jpeg


In-line fuse/circuit breaker thingy.
IMG_9173.jpeg


This is the right side of the 80A fuse. The larger white wire is connected to the positive terminal on the battery. The 3 red-blue wires go to other stuff that I haven’t fully traced out yet. All 4 of these wires are constantly hot the way they are currently wired.
IMG_9161.jpeg


With respect to the GM alternator, my plan was/is to hook the charging wire directly from the post on the alternator to the battery positive terminal. My questions are as follows:

1. What do I do with the original white wire that runs from the original alternator post, through the in-line fuse/breaker, to the left side of the 80A fuse? It seems as though I need to leave it connected to the left side of the 80A fuse because it splices into some other wires/circuits. Should I just disconnect the short section the goes from the alternator post to the in-line fuse/breaker, and make sure that breaker is covered/protected?

2. The factory alternator output is something like 60 or 70 amps. My GM alternator has a max output of 150 amps. Am I going to be popping this 80A fuse constantly? If so, what’s the permanent/right fix?

3. WTF is the purpose of the 80A fuse? Lol.
 
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the original white wire was on the charging post of the original alternator? You can put it on the charge post or the new alternator or move it to the battery.

you won't be blowing 80 amp fuses unless you have something wired in that pulls more that 80amps, Your alternator has 150 amps available. I would also change that to an 80 amp inline maxi fuse, slow blow. Hope that helps
 
Shreddinlettuce said:
Was it a diesel truck at some point? Could be for glow plugs?
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Nah. It’s always been a gas truck, as far as I know, and can tell. Im assuming the fuse box is interchangeable for both the gas and diesel models.

What I have gathered from my attempts at researching this is that the "Glow/AM1" fuse ultimately routes power to the ECU and the ignition system. I guess it acts as a "main power" fuse, if you want to call it that. If the circuit shorts out and blows the fuse, the truck won't start or run (from what I've read). I don't necessarily understand why the factory alternator charge wire is connected here, in lieu of directly to the battery.
 
Kickdeez said:
Nah. It’s always been a gas truck, as far as I know, and can tell. Im assuming the fuse box is interchangeable for both the gas and diesel models.

What I have gathered from my attempts at researching this is that the "Glow/AM1" fuse ultimately routes power to the ECU and the ignition system. I guess it acts as a "main power" fuse, if you want to call it that. If the circuit shorts out and blows the fuse, the truck won't start or run (from what I've read). I don't necessarily understand why the factory alternator charge wire is connected here, in lieu of directly to the battery.
Click to expand...
Most likely reduction of wire length/ cost
 
Jeff B said:
the original white wire was on the charging post of the original alternator? You can put it on the charge post or the new alternator or move it to the battery.

you won't be blowing 80 amp fuses unless you have something wired in that pulls more that 80amps, Your alternator has 150 amps available. I would also change that to an 80 amp inline maxi fuse, slow blow. Hope that helps
Click to expand...
Thanks! That is helpful!

Correct, the white wire was originally hooked to the charging post on original alternator. I thought about just hooking it to the charge post on the new alternator. But I want to use a bigger gauge wire. And some of the existing wiring is in questionable condition throughout. So I want to run a new wire anyway to eliminate any potential charging issues from potentially crummy wiring.

Here’s what im thinking…feel free to tell me if this is dumb.

1. Eliminate the short section of existing charging wire from the alternator to the existing inline fuse and make sure that fuse is covered/protected.
2. Run a new minimum 6 gauge (probably bigger) charge wire from the alternator to the battery positive with an in-line “slow-burn” fuse (I’ve seen others use like a 175A fuse here - not sure if that’s overkill, but it seems reasonable to me given the max output of the alternator).
3. Run a wire from the battery positive to a power distribution block to cut down on wire clutter to the battery.
4. From the distribution block I can run a power wire to the fuse box (80A AM1 fuse), power wire to the starter, power wire to the winch, and power wire to my “boom box”.
 
Kickdeez said:
Thanks! That is helpful!

Correct, the white wire was originally hooked to the charging post on original alternator. I thought about just hooking it to the charge post on the new alternator. But I want to use a bigger gauge wire. And some of the existing wiring is in questionable condition throughout. So I want to run a new wire anyway to eliminate any potential charging issues from potentially crummy wiring.

Here’s what im thinking…feel free to tell me if this is dumb.

1. Eliminate the short section of existing charging wire from the alternator to the existing inline fuse and make sure that fuse is covered/protected.
2. Run a new minimum 6 gauge (probably bigger) charge wire from the alternator to the battery positive with an in-line “slow-burn” fuse (I’ve seen others use like a 175A fuse here - not sure if that’s overkill, but it seems reasonable to me given the max output of the alternator).
3. Run a wire from the battery positive to a power distribution block to cut down on wire clutter to the battery.
4. From the distribution block I can run a power wire to the fuse box (80A AM1 fuse), power wire to the starter, power wire to the winch, and power wire to my “boom box”.
Click to expand...
really don't need a fused connection between the alternator and battery.

Would be best to use an amp clamp on the started cable and then on the other hot lead feeding the fuses for your other items so you know what the amp draw is with everything on.
Then you can add the 10% to that to get the amp rated fuses you need and have a well protected system. May want to think about breakers too,
 
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