[AT] Generator operation

[szabelski at wildblue.net]

Brad,

Hopefully this helps you to check out the regulator:

https://www.youtube.com/watch?v=II-6nOw28J8

The young lady in the video is very knowledgable about Farmall tractors, she’s done several books on them.

To me it sounds like the regulator is cutting out to soon. When the battery is charged, the one coil (assuming you have the older type with coils) that feeds the battery for charging will open and the current draw for the battery goes to zero instantly. That’s because it is either open or closed, no in between. The newer electronic regulators can allow the battery charge to slowly drop, or go to a trickle charge state, once the battery is charged or nearly charged.

17V out of the generator seems a little high to me. Usually you should only see 14V - 15V.  You only need to apply a charge of about 2V more than the battery rating in order to charge the battery. At 17V you could be causing the one coil to drop out early before the battery starts to charge. You may want to see if you can find the specs for the tractor and verify that you have the right generator with the correct size pulley.  The engine speed and the ratio of pulley sizes between the two determines how fast the generator spins. If it spins too slow, low output voltage. If it spins too fast, high output voltage.

Carl
----- Original Message -----
From: Gunnells, Brad R <brad-gunnells at uiowa.edu>
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Sent: Thu, 06 Aug 2020 23:31:34 -0400 (EDT)
Subject: [AT] Generator operation

Ok, see if I can help get this back on tractors.....

Dad has a very nicely restored Ferguson TO-35 that has a 12v generator with external regulator. I'm going to drive it this weekend with him (he's driving a Farmall 656) on a tractor ride. He mentioned a while back that it wasn't charging. So I went over and looked at it tonight.

I picked up some testing procedures from Yesterday's Tractor site and a few others. To make a long story short, I took a jumper wire and connected it to the mounting bolt on the regulator to the field connection on the regulator. It excited things and the amp gauge showed a charge. I had my volt meter (cheap Harbor Freight unit) on and it appeared to run up to nearly 17 volts before the regulator kicked out. We fiddled with things a while (put a load tester to draw battery down, etc) and while it will show a charge it makes me think the regulator may be suspect. It shows a 10 amp + charge when running at higher RPMs and then it suddenly drops to 0. I'm used to an alternator where the charge rate drops gradually to zero. Is this how external regulators typically run or is the regulator not working as intended? Good news is the generator is working so that's a plus.

Thanks for any insight from those of you who've worked with these before.

Brad