nj02z

iTrader: (6)

Wiring in this Moroso disconnect switch for cars with alternators.I am running 4 gauge from the alternator back. Will the small 10-32 lugs handle the amps from the alternator or does it need to be wired different? The alternator wire they call for seems small.

LLLosingit

iTrader: (4)

I looked up Moroso 74102 directions (not sure what part number you're dealing with) That has the same wiring diagram and it states "Use a 10- gauge minimum for this connection" It doesn't state a maximum only that it's "20 amp max"

nj02z

iTrader: (6)

Yes 74102

Nathaninwa

I have always wired that alternator setup to the field exciter wire that turns the alternaor on, the charge wire it self makes the junction at the starter

Someone sells a specific 300/175 amp dual **** off that will cut the charge wire separately

That would be a lot of voltage drop going from the alternator, back to the battery and then back up front to power up the car

nj02z

iTrader: (6)

So I can wire the alternator to the front junction with 4 gauge wire or run it back to the battery then run the small wire back to the cutoff switch?Thanks.

BOLO

iTrader: (40)

I ran a 4 gauge wire from the master disconnect switch to the alternator.
2 ga from master disconnect switch to starter.
2 ga from starter to positive junction box.
Make sure you have all your grounds.

nj02z

iTrader: (6)

Did you also kill the exciter wire at the master disconnect?

Nathaninwa

The trouble with these switches is the many ways people wire them and what the initial intended useage was for. The diagram shown I'll bet if for full race car, and depending on how it's wired, usually with a switch panel, the car will shut off. If the exciter wire isn't cut you'll get the run on situation

With the two small post style, I'll wire from battery to switch, from switch to starter, and junction from there to the alternaor or car side power

The alternaor I'll use the stock idiot light. I'll find it in the harness and reroute it back to the switch, then back forward to the alternaor. This way the car still stops with key, the idiot light still functions as normal and the field wire is cut when the switch is turned off preventing feedback through the ignition switch itself

And I agree with the grounds. Almost need to run a dedicated ground upfront to the block. Sheet metal and spot welds don't flow current all that well, and can create noise in efi setups

squarles67

I just run the big wire from the alternator right to the positive post on the battery, no need to go through the switch. Just put a adequate fuseable link or fuse close to the battery.

BOLO

iTrader: (40)

No exciter wire.

LLLosingit

iTrader: (4)

Doesn't that defeat the purpose of the master shutoff switch?

squarles67

No. Master shutoff kills power to everything so the engine will die if you hit the switch. The fuse protects the smaller wire to the alternator.

That switch says 20 amp max on that smaller terminal. On a street car you're going to have a whole lot more going through it than that.

Doug G

I ran 8ga from alt to battery and 00 welding cable to the switch and starter. no issues.

I'm also using a Ford solenoid so the starter wire is only hot during cranking

nj02z

iTrader: (6)

What gauge wire would you use for the exciter wire?

squarles67

Exciter wire doesn't take much, not really a load on it. 16 to 18 gauge would be more than enough I would think.

TTur1996

You guys do realize that If you have a wire going directly from the battery to the alternator it stays hot whether you throw the master disconnect or not. If for some reason something got hot and melted into that wire it would put power back to whatever melted to it and may not blow the fuse. You should have it on the Other side of the disconnect so there is absolutely no power going anywhere. And how would a 20 amp fuse survive with anywhere from 100 to 160 amps in our case when all the accessories are pulling way more than 20 amps? ( no we are not pulling 160 amps our alt puts out that much). But between the water pump, two fans, fuel pump, two stages of nitrous, two bottle heaters, and all the other stuff. There is no way a 20 amp fuse will hang. You will need a much higher amperage fuse to handle such a draw. In which case will be way harder to blow in the event of a weak short. The only way to do it right is to have everything cut at the main kill. Period.

TTur1996

We also use a Moroso disconnect for the alt only. And yes we have a 6ga wire going back to the car side of the master disconnect. The main charge wire hooks to both sides on the main lugs on the Moroso disconnect. And just a small switched fused wire going to the excite terminal on the Moroso. Then we can kill the alt when we get to the line with the flip of a switch, then flip it back on after the run to charge on the way back to the pits.

nj02z

iTrader: (6)

My alternator is tied to a junction up front.I want to run the exciter wire back to the Moroso switch and back to the alternator. I did not want to tie my alternator in to the battery side of the switch. So 16 gauge will work for the exciter wire?

TTur1996

That's what size ours is coming from a 20 amp fuse and switch.

Nathaninwa

I've used paired speaker wire before so make the run easier for the exciter