73 350 not charging

[salvageyard saviour]

Original prestolite alternator and external regulator.

A couple warm days here in Michigan, so I thawed the garden hose and started her up in a stand.
Recently rebuilt Quadra jet (working great) replaced engine harness (round plugs) installed original alternator and connected instrument cluster from boat.

Had it running for a bit checking carb settings, oil pressure and temp. Tach is acting funny and not sure volt meter is right either.
By the time I got multi meter to check alt output and battery, both at 7 volts engine running, soon after engine stalled.

I want to do a full field test. Is this a good starting point? How?

The back of the external regulator is pretty mushy and suspect it's bad, before buying one I'd like to know if alternator is bad or both. Might get a Sierra self regulating 1 wire if both.

 

[alldodge]

If charging is the only problem, I would get a one wire ALT and by-pass everything else

 

[salvageyard saviour]

Thanks for the reply,
I don't mind a 1 wire , I can still make it "Look " original by leaving the regulator bolted on but not wired.

A question about the self exciting alternator. I've read they need some rpms to start charging. Is that to only get the initial magnetism charge and it's good as long as the engine stays running?
I do a lot of idling trolling.

 

[bruceb58]

You can also do a 3 wire alternator. All you need to do is connect up an excite wire(from ignition), the main charge wire to the battery and the sense which you can just jumper over to the main charge wire.

You probably already have the ignition wire going to your present system.

 

[Scott Danforth]

I don't mind a 1 wire , I can still make it "Look " original by leaving the regulator bolted on but not wired.

why?

i would get a 3-wire alternator and modify the harness. external regulator alternators went away with the dodo bird

 

[salvageyard saviour]

why?

i would get a 3-wire alternator and modify the harness. external regulator alternators went away with the dodo bird

Why?
Just for looks. Even if it's not doing anything.
The thermostat housing just looks empty without the regulator there.

 

[salvageyard saviour]

Been looking for a 3 wire.
The mounting bracket is a 70's style for the old prestolite alternator with the 2 ears that fit outside the bracket.
The only one I can find that will fit is Arco or Sierra 1 wire.

I have a 80's style bracket that fits the Delco alternator, but I put it on a 78 truck block and had to modify it to keep the alternator low under the exaust manifold. I'll have to look again, might have been a different reason. But I did have to grind and drill.

Should I do the same thing here to be able to use a 3 wire? Or will the 1 wire be okay?

 

[Scott Danforth]

post a pic, or visit your local alternator shop

 

[salvageyard saviour]

80's style Delco

(Automotive 10si at right but mount the same as marine)

70's style prestolite

(Second pic is a Motorcraft but shows the 2 ears for mounting similar to prestolite)

Looking at prices, I can buy new regulator both diode sets and brushes for less than a new mount. Add slip rings, bearings and stator still less than a 1 wire.

If it looks too rotten inside when I take apart, I'll get the 1 wire and get used to revving after start up.

 

[salvageyard saviour]

Update:
Works great after repairing old prestolite.

New service manual showed how to full field to confirm bad alternator. Manual also described how to test diodes, all 3 positive bad.
$20 for diodes and brushes. 14+ volts now.
Installed new regulator even though old one was still working.