Farmall B won't charge

nguerra

New User
Ok so I have a bit of a problem here. I have a friend who has a gorgeous Farmall B. The same tractor his grandfather had that he used to ride on the rear axil as a kid. He?s done a beautiful job restoring it and its been in local parades for the last 10 years running just fine. A couple of years ago he started replacing the original light switch, regulator, and amp meter, but never finished it. As he?s getting up there in years and has had some health problems I?m trying to step in and help, although I?m not familiar with tractors. I?ve been reading through the forums on this subject and I believe that I?ve read and understand John T?s instructions for determining the cause of the problem. The problem is that after following the test and measurements the conclusion according to the flow chart is that the generator needs to be repaired or replaced. I did remove the generator and sent it off to a repair shop only to receive it back again with a call from the shop stating there is nothing wrong with it. So after retesting and coming to the exact same conclusion, I wanted to ask you the experts what do you think? Here is what I have and done so far.

Farmall B 6V positive ground

A terminal of the generator connects to the GEN tab on the bottom of the regulator

F terminal of the generator connects to the F tab of the regulator

BAT tab of the regulator goes directly to the (+) terminal of the amp meter

L tab of the regulator goes to the light switch and ignition switch

Extra wire (yellow) goes from the base of the regulator to the frame ground bolt where the + terminal of the battery goes

<image src="http://forums.yesterdaystractors.com/photos/mvphoto8546.jpg"/>

<image src="http://forums.yesterdaystractors.com/photos/mvphoto8547.jpg"/>

With tractor off, turning the light switch to ?D? provides a ~10-amp discharge on the amp meter

With tractor off, turning the light switch to ?B? provides a ~12-amp discharge on the amp meter

With ignition switch on (light switch to ?O?) provides ~2-amp discharge on the amp meter

So, I believe that the amp meter is correctly wired and working as should

Measuring the voltage between the frame and meter I get 6.38V on both amp terminals

<image src="http://forums.yesterdaystractors.com/photos/mvphoto8548.jpg"/>

With tractor off, I run a jumper from the BAT tab of the regulator to the A terminal of the generator to polarize the regulator and I do get a small spark. (video link below)

With the tractor running at low idle, both contacts of the regulator spark causing no charge to the battery. (I?m assuming there is not enough output from the generator to cause the relay closure)

Increasing the idle causes, the relays to close and thus forces the amp meter to peg the needle to the discharge side. (video links below)

Shorting the F terminal to the frame produces no change

Shorting the F terminal to the frame and shorting the GEN tab to the BAT tab produces no change.

From the pictures and videos, I?ve provided, is it possible that the generator repair center didn?t know how to test?

One other thing. With the tractor, off and the belt removed from the generator, I can cause the generator to run like an electric motor by manually closing the regulator relay. Then if I remove the F terminal from the regulator, the motor with stop and spin in the opposite direction.



Video 1 https://youtu.be/pqPq18hjDYg

Video 2 https://youtu.be/qP_qGu-k9bQ

Video 3 https://youtu.be/Ir9kCbvRclA

Video 4 https://youtu.be/HYfFssZOgLk
 
Two things pester me about what has been said in your post. One is that the spark when polarizing the ((generator)) was small. It is usually quite large and a bit scary. It takes a solid 12 gauge wire and about 1 full second of contact. The second thing is that the regulator cutout relay is arcing. They almost never do that. They either do not pull in to create a armature to battery connection through the ammeter, or they latch in and stay latched from being current welded in place. Are you sure the VR is for Positive ground. Jim
 
I am wondering about the field windings. To see if they are internally grounded (should not be) it is necessary to disconnect both the A and F terminals, then lift the field brush (if 3 brush) or the Armature brush if 2 brush, with a chunk of plastic between the brush and commutator, the field should now be disconnected from ground. A ohms test from ground to the F terminal should show open, infinite ohms. If shorted to ground, it will be low or no ohms. The measure from the A terminal to the F terminal should show about 2 ohms or so (again with the brush raised, and the terminals disconnected. Jim
 
old test when the field is grounded it means the gen is not working start there and ALL componets need ground to the frame of the tractor
 
jim, a few years back you helped me with my farmall h that just plain would not charge. off the tractor, everything checked out fine. genny would motor correctly. install everything back on the tractor, no good. turns out one of the wire terminals on the genny case would short out when the wire was installed, irrc it was the a terminal. the insulation around the stud was getting bad and when the wire was installed and tightened, it would short to ground. when you told me to isolate the brushed from the armature......whalaaa!!!!! that was the problem!! still charging good!!!
 
Thanks. Analysis by internet braille can be a challenge. Thinking inside someone else's thoughts/words to diagnose what they are trying to describe is an interesting mind game. Jim
 
Voltage regulator states right on the cover that it is a 6-volt positive ground. The video link below shows the amount of spark and how long I left it on the contact. If I increase the throttle to full speed the contacts on the VR close causing the amp meter to peg the discharge side of 0. Even when I turn the tractor off, the needle stays to the discharge side because the contacts are stuck closed. Not sure if I would say they are welded but closed enough to prevent the spring from pulling them back until some time goes by or I manually push them down. I will give the resistance measurement a try as soon as I can get back up to where this tractor is stored. I do recall doing a test I saw on a youtube video that disconnected the A and F terminals of the generator and then ran the tractor while measuring the voltage from each terminal to the frame ground. I just can't recall what the measurements were but they hovered right around 1 Volt.
 
jim, when i re-read the op post it said in the motor test the genny motors, but then when the field is disconnectd, the genny stops and reverses direction. all the ones i motor test the speed up, not reverse direction. that seems odd.
 
I'm not sure when I can get back to the tractor as its about a 7-hour drive away. From what I've provided, is there enough information to say for sure that the generator has a problem? What I'd like to do is order parts before I leave in order to do the repair while I'm there.
 
By a used one that works from Ebay, and have the original rebuilt. What is likely wrong may quite possibly be difficult to fix without big soldering equipment. This solution prevents traveling grief. Jim
 
Finally back up in Northern MI and had a chance to take some resistance measurements for you. With the connections to terminals A and F removed and 3 brushes lifted with plastic to prevent contact to the commutator, I have the following measurements.

F terminal to chassis open
A terminal to F terminal open

I'm guessing from your post that the 2 ohms that should be present between the A and F terminals is a problem. Would this still point to bad field coils? Not sure how the connections are internal to the generator.

Just another bit of information even though I don't think this would matter but since I'm not familiar with tractors. The positive post of the battery was disconnected from the frame during these measurements.
 

I was looking at the post provided by the following link http://www.yesterdaystractors.com/articles/artint4.htm
From what I can tell, I don't see how I would receive 2 ohms unless the brushes are touching the commutator so if that is true, does anyone see any issues the generator?
 

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