Bench testing 10si gm internal regulated alternator

[flatheadvff]

I use 10si internal regulated gm alternators on most of my tractors. I use the 3 wire versions, not the 1 wire as most tractors don't spin fast enough and have trouble energizing. I have a 1 wire on a tractor I recently bought and it isn't working. Switched it out with a 3 wire I had on the shelf from a rebuild shop family has been using since the 60s. Hooked up my wires and it still doesn't work. Disassembled both alternators and tested components, which test good. Only thing I don't have tool to test is the regulators. (Had one back in the day but can't seem to locate it). Growing up in a parts store and garage, I remember that one could ground a point in the back of the alternator and get unregulated charge. This would let you know if the alternator was able to charge and that the regulator was most probably bad. Problem is I don't remember where said point to ground is. If anyone knows I would appreciate the Information and a picture would be, as they say, worth a thousand words. Thanks LJS

 

[wore out]

I use 10si internal regulated gm alternators on most of my tractors. I use the 3 wire versions, not the 1 wire as most tractors don't spin fast enough and have trouble energizing. I have a 1 wire on a tractor I recently bought and it isn't working. Switched it out with a 3 wire I had on the shelf from a rebuild shop family has been using since the 60s. Hooked up my wires and it still doesn't work. Disassembled both alternators and tested components, which test good. Only thing I don't have tool to test is the regulators. (Had one back in the day but can't seem to locate it). Growing up in a parts store and garage, I remember that one could ground a point in the back of the alternator and get unregulated charge. This would let you know if the alternator was able to charge and that the regulator was most probably bad. Problem is I don't remember where said point to ground is. If anyone knows I would appreciate the Information and a picture would be, as they say, worth a thousand words. Thanks LJS

In the photo, a screwdriver is inserted into the "D"-shaped hole in the back of the alternator to ground a tab on the voltage regulator to bypass it.

The tab is just a short distance inside, don't "miss" it and insert the screwdriver too far, it will contact the moving rotor inside and things will get ugly!

 

[flatheadvff]

Awesome, thank you. Great picture.

 

[wore out]

In the photo, a screwdriver is inserted into the "D"-shaped hole in the back of the alternator to ground a tab on the voltage regulator to bypass it.

The tab is just a short distance inside, don't "miss" it and insert the screwdriver too far, it will contact the moving rotor inside and things will get ugly!

To be clear, I should have stated that the "tab" is on the brushholder.

View of the tab from the other side.

 

[flatheadvff]

I have 5 extra alternators. 3 of which I paid for a busines, that my dad has been dealing with since the 60s, to fix. Not a one of them worked. I just knew there was something I was missing. I pulled out a 70s repair manual and the middle of 3 pages dealing with 10si alternator was torn out, lol. Went and bought a new alternator put it on and wha la. So apparently I'm not so out of touch after all. Just couldn't believe that not one out of 5 worked.