[AT] Generator operation

[Jim Becker]

Don't believe everything you see on youtube either.  Right off the top, one 
of her tests is to unhook the battery on a running engine.  It is dangerous 
and proves nothing that can't be easily tested otherwise.  I warned the 
publisher about this before the book was published, but they didn't fix it. 
To get the same information: stick a voltmeter on the battery and see what 
the reading is not running.  Start the engine and check again.  If the 
reading increases, it is charging.  If it remains the same or goes down, it 
isn't charging.

The 17 volt reading and sudden change in charging both suggest a sticky 
voltage regulator contact inside the regulator.  This is the one normally 
closed when the engine is off.  You could try cleaning the contact (kraft 
paper of file, no abrasive board or paper).  Make sure the regulator is well 
grounded.

One comment on volt meters, the cheap digital meters are susceptible to 
electrical noise, which old tractor ignition and charging systems produce 
much of.  You can get wrong or random, rapidly changing readings.  You need 
to either use a high quality digital meter or an analog.  Cheap analog 
meters generally tolerate the noise and work OK.

Jim Becker

-----Original Message----- 
From: szabelski at wildblue.net
Sent: Friday, August 07, 2020 3:23 PM
To: Antique Tractor Email Discussion Group
Subject: Re: [AT] Generator operation

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

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