one wire alternator

Ok nice to know I have a 70 Rebel SST Wagon that needs a alternator & battery. I am thinking about going with 80-100 amp alternator & MSD ignition coil & new voltage regulator. Just want something to handle everything so I wont have lights dim etc.. Would a 80 amp alternator be safe to put on it? Its the only thing I see local that is new & not reman. The alternator that is on the car the wire is broke & bolt hole messed up on it so I was just going to replace it with a new one. I am also going to go with 4 core radiator & looking to see if a trim line cooling fan will fit behind the radiator. I have the AMC 360 2 bbl.

Edited by kalve - Nov/19/2017 at 10:39am

Delco alternators are Y wound. Y wound alternators do not put out well at lower RPM. My Rebel Machine's 1 wire Delco (NOT my install. It was there when I bought it) dims the lights way down at idle. I plan to restore the stock Motorola setup in the future.

Delta wound alternators, like the stock Motorola alternators put out much better at low RPM due to the windings being in parallel as opposed to being in series like the Y wound units.

OK, back on alternator stator wiring methods............



Edited by billd - Nov/20/2017 at 9:22pm

73hornut wrote: vinny wrote: Just curious, how do you know it doesn't charge at idle and how much do you have to increase the revs to make it charge. On my 10si's the light only came on when the engine ran really slow and probably an extra 25 RPM might have been enough to put it out. Volt gauge drops to 12 at idle and goes up to 14.5 with a few hundred more rpm. idle is about 700 rpm. Volts go up when in park and idle is higher. In gear with fans on and lights and wipers, volts are just below 12.

The 10si is a different animal and is not a "one wire alternator".

That's pretty low at idle - but 14.5 sounds about right otherwise. 
So either you are experiencing the side effect of that particular version of someone's single wire alternator mod or there's a problem such as a diode bad/going bad, or slipping belt, etc. A belt that isn't gripping can still spin it enough to give you the needed voltage at higher RPM as the percentage of slip would be most notable at idle speeds. A 10% slip at 700 means a 70 RPM drop, down to 630 RPM - (just rough simple figures grossly over-simplifying things!) but that same 10% at 1500 RPM means it's still spinning at 1350 (I know, I know, not accounting for pulley size and ratios etc.)
Similar in how a bad diode could impact things.
On the other hand, I'm not sure how those single wire regulators all function - each is a bit different (they are not GM/stock) so it's possible that unless it was better when brand new, you are experiencing the side-effect of the beast. There is no external excitation circuit, and some actually have the terminals 1 and 2 bridged so you can't connect any light circuit or sending to them. 
Alternators have their rotors treated so they don't hold residual magnetism - unlike generators. They depend on something feeding that field to get them started charging - unless you hit high enough RPM and then what little magnetism there is can get them going. 
This is one reason the "single wire" setup works on tractors - how often does anyone idle a piece of ag or construction equipment? You start it and shove the throttle lever ahead and get to work, so there's never an idle charging issue to worry about. 
I'd have to look at the schematics and wiring of a couple of different single wire type regulators to see if I can see something that might stick out or jump out at me. 

That was one of the possibilities I mentioned.......... in a NORMAL alternator the diode trio would supply field current via the regulator and if it's bad, it can cause issues.
A bad diode can lead to "restricted output" or lower output at lower speeds because it's operating at only partial capacity. A scope would reveal that. Otherwise to properly test the diodes without disassembly a real tester is needed as the stator windings will cause false readings.
A bad diode - either shorted, open, or weak, would show on a scope pattern.