65 Massey Ferguson generator, voltage regulator, volt meter

jedagi

Member
My tractors volt meter gage started showing negative 8 volts. I removed the battery cable for a few seconds then put it back on the battery post. The gage shows charging, up to 14 volts depending on rpm. But after a few minutes the volt meter will drop back to negative 8 volts.[/quote]
 
This is a bit curious to me, as there isn't a volt gauge (2", dash mounted) that I know of that will read negative voltage. Most of them go from 8 to 16, and they all indicate "positive" voltage. Anything less than ~12.8 when running indicates a discharge, and anything over 14 is an overcharge.

The other thing is that all the MF65's were factory equipped with an amp meter, not a volt meter, so yours may or may not be wired correctly.

I assume this is a diesel, so disconnecting the battery isn't going to kill the 'spark plugs'. I am also assuming that it has the original Delco generator and voltage regulator. Is that correct? Did it previously work ok and did this just start happening?

I think we need a little more info to go on.
 
My apologies. I restored this tractor a couple years ago and i replaced a couple of the gauges that was busted. The only gauge i could find at the time with a stainless bezel was a volt meter. And you are correct about the negative eight volts. I was thinking one thing and typing another. The gauge drops back to below 8 volts. Remove the battery cable then put it back and it starts showing over 12 volts.( normal ) depending on rpms. Its worked fine for the last couple years until about two weeks ago. When i restored it i also replaced the voltage regulator that i bought from this website. I thought the issue might be in the regulator but i thought i would ask the question on here before i started tampering with it.. And yes its a diesel, 1964 MF 65 row crop type tractor.
 
Ok, that makes a lot more sense. Thanks.

From what it sounds like, at "no load" on the generator, it puts out correct voltage, but when it starts working to charge the battery, it shows discharge, right? That indicates that the fields are energized via the regulator, but the rotor isn't putting out under load.

First thing I'd check, is the brushes and brush springs in the generator. It sounds like one or more is 'floating' - either worn out, or brush holder 'stuck' and not providing tension on the brush to commutator.

Do you have a multi-meter?
 
Jed, I had the same problem when i restored my
tractor (135) I also bought a new regulater from
Here. Found out it had to be energized. Take a piece
of wire and put it on the positive side of the
battery then take the other end and spark it across
the field side (+)of the genarator terminal this
should fix you up. Worked for me when i was told to
do it. It might take a couple time of sparking it
across Just FYI
 
(quoted from post at 02:49:39 02/25/15) Jed, I had the same problem when i restored my
tractor (135) I also bought a new regulater from
Here. Found out it had to be energized. Take a piece
of wire and put it on the positive side of the
battery then take the other end and spark it across
the field side (+)of the genarator terminal this
should fix you up. Worked for me when i was told to
do it. It might take a couple time of sparking it
across Just FYI

thanks, ill try that.
 

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