Magnum swap using Magnum alternator

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Evan Dutch

Evan Dutch

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Hey guys,

Working on finishing up my magnum swap in my 1971 Scamp and I’ve got something I need help with. I am running the magnum serpentine belt setup so I will be using an alternator that came factory on this magnum engine. My battery will be in the trunk instead of under the hood.

My question; this alternator is rated for 90amps. My ammeter will be bypassed, this is not a one wire alternator so I plan on using the two field wires like the original alternator did. Is this amperage rating too much for the car even if the ammeter is bypassed?

Also, would anyone be able to tell me where the black wire that attaches to the back of the alternator goes once it passes through the ammeter? I know it needs to be returned to the battery to compete the charging circuit.

I also plan to use a circuit like the one @crackedback has designed. But I am unsure how to get it to work with my application since it is drawn using a 1 wire alternator.

Any help would be greatly appreciated!

Thanks

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So far as I know that will work. There is a website that sells a kit to replace the original "in the computer" VR with a flat one used on 70/ later cars.
 
67Dart273 said:
So far as I know that will work. There is a website that sells a kit to replace the original "in the computer" VR with a flat one used on 70/ later cars.
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Would there be an issue seeing that my alternator is not a one wire setup as shown in the diagram?

You wouldn’t happen to know where I could find this new voltage regulator would you?
 
My car uses a universal cheapie harness so it is a bit different but I just wired the 70's regulator to the later stock magnum alternator.
 
Evan Dutch said:
Hey guys,

Working on finishing up my magnum swap in my 1971 Scamp and I’ve got something I need help with. I am running the magnum serpentine belt setup so I will be using an alternator that came factory on this magnum engine. My battery will be in the trunk instead of under the hood.

My question; this alternator is rated for 90amps. My ammeter will be bypassed, this is not a one wire alternator so I plan on using the two field wires like the original alternator did. Is this amperage rating too much for the car even if the ammeter is bypassed?

Also, would anyone be able to tell me where the black wire that attaches to the back of the alternator goes once it passes through the ammeter? I know it needs to be returned to the battery to compete the charging circuit.

I also plan to use a circuit like the one @crackedback has designed. But I am unsure how to get it to work with my application since it is drawn using a 1 wire alternator.

Any help would be greatly appreciated!

Thanks

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View attachment 1716138273

View attachment 1716138274
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The wiring you showed will work fine as long as you bypass the ammeter. The large charge cable from your altern Will be the one in that diagram.

You need to get an electronic voltage regulator like used on most 70s Mopar cars and trucks. One small field wire of your alternator goes to the regulator. The other small field wire goes to a fused ignition source.

This electronic regulator must be case grounded to the body. Most currently available regulators are hit-and-miss for quality. Mine was overcharging. I think someone was selling used and new old stock good quality regulators and maybe he still has some. Maybe it was @halifaxhops
 
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Bobzilla said:
The wiring you showed will work fine as long as you bypass the ammeter. The large charge cable from your altern Will be the one in that diagram.
You need to get an voltage
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So I can bypass the factory wire that runs to the alternator outlet entirely? And run a wire directly to the battery?
 
Basically yes, bypass the factory output wire so charge current does not go through the bulkhead connector and ammeter to power the car. The factory system is already prone to cause fires. The bypass setup, both ammeter and a new charge circuit will help prevent that.
 
Bobzilla said:
Basically yes, bypass the factory output wire so charge current does not go through the bulkhead connector and ammeter to power the car. The factory system is already prone to cause fires. The bypass setup, both ammeter and a new charge circuit will help prevent that.
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How will the rest of the car receive power if the original alternator output is bypassed?
 
You will still connect the rest of the car as usual. The old setup had the main charge wire going through the bulk head, through the ammeter, and then to everything in the car. When you make a new charge wire going from the alternator to the battery you are making sure all high amp charging goes through the new circuit that is large enough to handle it.

Next you bypass the ammeter using one of the methods you find out there on the interweb (this site). When you do this you are not just disconnecting it, you are bypassing the ammeter or doing a voltage gauge conversion, but you keep the the rest of the car powered up otherwise the same way.
 
Here is the sale thread I was referring to for voltage regulators. If you want to check with him do it through that sale thread so we don't break any site rules. The picture shows the style of regulator you would want to use, but you want one that is decent.
[FOR SALE] - voltage regulators
 
Bobzilla said:
You will still connect the rest of the car as usual. The old setup had the main charge wire going through the bulk head, through the ammeter, and then to everything in the car. When you make a new charge wire going from the alternator to the battery you are making sure all high amp charging goes through the new circuit that is large enough to handle it.

Next you bypass the ammeter using one of the methods you find out there on the interweb (this site). When you do this you are not just disconnecting it, you are bypassing the ammeter or doing a voltage gauge conversion, but you keep the the rest of the car powered up otherwise the same way.
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Oh nice, I’ll probably do a voltage gauge conversion, I’d like to keep an eye on charging system status
 
Im going to be using 1/0 gauge Wire from the battery to starter. And 4awg from the alternator to the battery. What size wire should I use for the part of the diagram that runs the wire from the master cutoff switch to the mopar starter relay?
 
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