Fixed 3 Brush 6 Volt Generator Motor Test

[wrg4257]

I have a 1939 Farmall H. It runs fine but the charging system has never worked properly. Before I retired I had a professional come out and "fix" the charging system. Keep in mind this was before I understood the inner workings of the 6V positive ground system.
When he was done I had a rebuilt 6V generator and he replaced the cutout switch with a VR. It never dawned on me to have him show me 1) the ammeter readout showing charging, or 2) to put a volt meter on the battery to show me 7.2 volts while the tractor was running.
Now that I am retired I have time to dig into the charging system and find out why it's not charging. I've used most of this forum to gather testing techniques and trouble shoot my charging system. I am the point of conducting the motor test to see if the generator is working. I took the generator apart per forum instructions.
What I found was that the inners looked new with the exception that the commutator bars were tarnished. I buffed them carefully and put the generator together.
I should note at this point that my 3 brush wiring looks different that the diagrams I have found on this site. My field wires go from the F terminal and end at one of the main brushes, not the third brush. And then A terminal goes to the third brush.
When I conducted the motor test. I attached the pos battery to the generator case, grounding the F terminal to the generator case. Then I connected the neg side of the battery to the A terminal and the generator spun. Then I disconnected the grounded F terminal expecting the generator to speed up, but instead it stopped and reversed direction.
This is where I need help.
Thanks,
WRG

 

[Steve@Advance]

That you got the gen to motor, I would consider that proof it is good, regardless of the direction.

The wiring you are describing doesn't sound right.

Here is a diagram, it's on the internet, so it has to be true! LOL
H Wiring

 

[John T]

Sounds to me like your genny is wired bass ackwards. The main fixed UNGROUNDED brush is 180 across from the fixed GROUNDED brush and it wires to the gennys ARM post. The Field is wired to the third adjustable brush, through the field coils, then out to the gennys FLD post. That way the closer the adjustable brush is to the main fixed ungrounded brush the more the field current and the more charge.

A goes to the fixed ungrounded brush (180 across from fixed grounded brush) NOT the third adjustable brush

Once she's wired correct follow my troubleshooting procedure to determine the cause of non charging.

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=jd&th=458743

Maybe the other gents can add more to this ?????

John T
John Ts Charging Troubleshooting

 

[J. Schwiebert]

I am a little confused on your test. You need 3 wires to make the motor test. Positive or negative ground makes no difference to a generator, it does to the regulator. Hook one wire to a battery post ( + we will say and the other end to the F terminal) Hook the other cable end to the A terminal and the other end to battery negative post. The generator should turn like a motor. Now take the third wire ground one end to the field terminal and the other end to the generator case itself. The generator should slow down. If not you have e-mail? J.

 

[J. Schwiebert]

I forgot to tell you when the third brush generator is wired correctly the 2 wires cross. Also read John T's post very carefully and follow it!

 

[wrg4257]

Thanks to all for the good feedback. I've used John T's help before and look forward to going through it tomorrow.
I'll come back when I know more.
WRG

 

[wrg4257]

Well it's a new day; a day my ammeter moved!
I changed the wiring in the gen to match diagrams. Then I reran the motor test with positive results.
So I put the gen back on the H and started to go through John T's trouble shooting steps.
I was getting pretty depressed until I got to #6 under the heading "To Determine It Its a Gen or VR Problem".
I used a remote started cable to connect the Vr's BAT and ARM terminals. With the tractor running I pushed the button and the ammeter showed charging. It didn't stop to record the value, but it must have been somewhere between 5 and 10 amps.
Question: should I try to trouble shoot/fix the cutout relay, or just invest in a new VR?

Thanks,
WRG

 

[John T]

Sometimes if the relay contacts are burned and pitted and sticking or else not making a good low resistance contact, you can lightly clean/buff/polish them to get them working. HOWEVER once the shiny silvery coating is gone they are prone to failure. It wont hurt to clean/buff/polish the cutout relay contacts because if they're not too bad and mostly oxide coated (NOT all burned and pitted) it may cure the problem.

NOTE the VR or cutout relay needs a good ground to work correct. Try a jumper wire from its metal base to a good clean ground and see what happens ?????????

John T

 

[wrg4257]

(quoted from post at 09:25:00 05/11/17) Sometimes if the relay contacts are burned and pitted and sticking or else not making a good low resistance contact, you can lightly clean/buff/polish them to get them working. HOWEVER once the shiny silvery coating is gone they are prone to failure. It wont hurt to clean/buff/polish the cutout relay contacts because if they're not too bad and mostly oxide coated (NOT all burned and pitted) it may cure the problem.

NOTE the VR or cutout relay needs a good ground to work correct. Try a jumper wire from its metal base to a good clean ground and see what happens ?????????

John T

I found the inners of the VR to be clean, very clean. The CO Relay and VR points looked good, but I buffed them litely with 400 sandpaper anyway.
I did some continuity testing and found a broken wire on the VR side of the two units.
It's a tiny silver wire about 1/2 inch long and connects the base of the VR (connection to "F" terminal) to a stub on the side of the VR. Both ends of this little wire are spiral bound to stubs, no solder, no screws.
The break in the wire appears to be from melting.
Any help would be appreciated.
The voltage regulator was made in Canada. Other than that there are no marks on it. I looks like a Delco Remy ABC153 and has a saddle mount bracket to connect it to the generator.

Thanks for your help.
WRG