MCI 8 Alternator field test???

[Jnbroadbent]

I have nothing to add other then the day mine goes out, i'll fab up a mount for a new one from auto zone. Seems easier!

But good luck.

[DEMOMAN]

Ok, here is the latest update on the alternator.  My bad gear driven alternator has 50 on the ID tag.  I received a lot newer donor 50DN alternator which is pulley driven (90s vintage).  I pulled the field out of it which has 3.3 ohms of resistance.   

     I see that my 50 alternator has one field stud only.  The 50DN has two field studs, F1 and F2 which are both ends of the winding wire.  F1 is the outside or "end" of the winding and F2 is the inside or "start" of the winding.   The F2 stud was grounded with a ground strap. 

     I'm assuming the 50 alternator's field has one wire to the F1 stud and the other wire connected to ground on the inside of the alternator.  I will have to use the diode frame and cover from the 50DN because the field is different. 

     I was told that I have to make sure the ground strap is hooked up the same way as my old alternator or it won't work but which stud do I hook the strap up to?  Wait and see which end of the winding is connected to what and follow suit?

Thanks for your input everyone!

Eric

 

[DEMOMAN]

Ok, I've taken the 50 alternator apart.  Field OHM tested ok at 3.3 when it was out.  It looks like something else was the culprit.  The stator had a bit of a short which threw copper BBs all over which must have been giving me the low OHM readings when it was together.  (see picture below)

     As far as the field wire and ground strap placement on the 50DN, (2 studs, F1 and F2) compared to the 50, (1 stud, F1); the second field wire was terminated on the field body, (ground) so it was easy to figure out which way to connect it up.

     All is well and producing 27.2 Volts!   

Thanks again everyone for all of your input!

Eric   

[bevans6]

Good job well done!   You might think about adjusting the voltage up closer to 28 volts, the batteries want around 14 volts each for a good charge.

Brian

[DEMOMAN]

Brian,

     I adjusted the voltage regulator to 27.2 volts with a load on it so it may be producing more than what I said.  The maintenance manual suggests adjusting it to 27.2 volts with a 20-200 amp draw with the idle at 1000 RPM so I turned on the bus heat, lights and drivers defrost and kicked it in high idle.  I figured that would be enough draw and RPM. 

     I'll check voltage next time I fire it up to see where it's at.   

Eric