851 voltage regulator problem

JOHN'S FORDS · Apr 3, 2015

I have a 1958 ford 851 with an 6 volt generator, I replaced the voltage regulator and polarized the gen. per instructions for a internally grounded field system (remove field wire and touch to bat terminal, reconnect field wire) The reg. is FAG10505A. I started the tractor and it was charging; the third time I ran it stopped charging. Put in another new regulator (different brand) and the same thing, worked the first few times and stopped charging. Can someone tell me what is causing the regulators to fail. It seems to be wired correctly.

JMOR · Apr 3, 2015

(quoted from post at 21:16:52 04/03/15) I have a 1958 ford 851 with an 6 volt generator, I replaced the voltage regulator and polarized the gen. per instructions for a internally grounded field system (remove field wire and touch to bat terminal, reconnect field wire) The reg. is FAG10505A. I started the tractor and it was charging; the third time I ran it stopped charging. Put in another new regulator (different brand) and the same thing, worked the first few times and stopped charging. Can someone tell me what is causing the regulators to fail. It seems to be wired correctly.

ou do know that the function of the VR is to cut back or even stop charging the battery when it is fully charged, do you not? All may be normal.

JOHN'S FORDS · Apr 4, 2015

(quoted from post at 21:00:29 04/03/15)

(quoted from post at 21:16:52 04/03/15) I have a 1958 ford 851 with an 6 volt generator, I replaced the voltage regulator and polarized the gen. per instructions for a internally grounded field system (remove field wire and touch to bat terminal, reconnect field wire) The reg. is FAG10505A. I started the tractor and it was charging; the third time I ran it stopped charging. Put in another new regulator (different brand) and the same thing, worked the first few times and stopped charging. Can someone tell me what is causing the regulators to fail. It seems to be wired correctly.

Click to expand...

ou do know that the function of the VR is to cut back or even stop charging the battery when it is fully charged, do you not? All may be normal.[VO/quote]Battery voltage is going down when running and engine stops when battery cable is removed.

JOHN'S FORDS · Apr 4, 2015

(reply to post at 05:15:46 04/04/15) Battery voltage going down when running and engine stops when battery cable is removed.

JMOR · Apr 4, 2015

If I were there, I would try to verify that all was well, in the absence of the VR. First by eliminating the VR regulator function, by installing a temporary jumper between ARM and Field, which shorts across/connects the internal field contacts of the VR and should result in full output all the time (assuming the VR's cut out is fully functional). Next, if that produced no charge, I would leave that jumper in place and ADD another jumper from the BATT to ARM terminal of the VR, which will simulate the closing of the cut out contacts. Don't leave these connected with engine off . If one or both yield full charge as you operate tractor, then I would consider that the VR was proven a problem and the generator & wiring is all good. 3 bad VRs does raise questions. Also, verify that the ground wire from the VR case to generator case is connected.

ErnieD · Apr 4, 2015

There was a design change during 801 production. I was going around and around between the VR and the generator. Rebuilder wanted both units to look at
made it right. Worked after that.

souNdguy · Apr 4, 2015

Full field and motor test Genny..

Can test very with 2 bats, charger and ammeter.

JOHN'S FORDS · Apr 4, 2015

(quoted from post at 14:05:39 04/04/15) Full field and motor test Genny..

Can test very with 2 bats, charger and ammeter.

Inst. i have for testing VR gave me these results:
test 5: jump arm to bat = no change in charging rate
("if test 5 does not correct trouble make this test")
test 6: jump fld to bat = charge rate increased to over 7 volts tested with a voltmeter connected to battery.
("if charging rate increases replace regulator")
The 2 replacement reg failed charging after a few times running.
Could a problem with the gen be causing the reg to fail?

souNdguy · Apr 5, 2015

Ensure the generator, vreg, and battery/chassis all see the same good, ground.

Your field circuit sounds open. Unless there is excessive field current or a field fault producing that, probably nothing the Genny did, though
faults in field wiring betwixt gen and reg could play a role.

JOHN'S FORDS · Apr 9, 2015

(quoted from post at 09:32:57 04/05/15) Ensure the generator, vreg, and battery/chassis all see the same good, ground.

Your field circuit sounds open. Unless there is excessive field current or a field fault producing that, probably nothing the Genny did, though
faults in field wiring betwixt gen and reg could play a role.

Turns out their was a short in the generator field coil drawing excessive current causing the regulator failures. Brought the generator to a re-builder that really knows old school and he replaced the field coils. Everything works fine now.
Thank you everyone for helping with this problem.

souNdguy · Apr 9, 2015

yup.. field faults will eat a B circuit reg.

851 voltage regulator problem

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