The Generator on my MT is not generating. It works fine as a motor (2 speeds as expected) but doesn't generate even when the armature wire is removed (I expected a no load voltage, I could be wrong there). This tractor uses a cutout relay but not getting anything from the generator. Ammeter shows discharge when lights are on and battery voltage slowly drops while running. I followed John T's troubleshooting guide but am at a loss. Is it possible that it motors fine but there is too much brush wear to generate? Any advice is appreciated.
- Thread starter mtn199
- Start date
Typically if it passes BOTH my motor tests it will charge. YES if you dead ground
the gennys FLD post that by passes the light switches Low High control (provides
resistive or direct path to ground IF SWITCH IS WELL GROUNDED) and calls for max
charge and there should definitely be open unloaded voltage on the ARM post way above
7 volts. With FLD post grounded and at fast RPM with no wires on the ARM post what
voltage are you getting ?????? If its good there next the Cutout Relay has to latch
closed (IT needs a good ground to work) so the battery can get a charge. Its hard to
believe theres not high voltage on the ARM with nothing attached if it passes BOTH
motor tests ??????? The light switch can be bad or not well grounded or the cutout
relay may be bad or not well grounded or its not wired right, BUT YOU GOTTA GET HIGH
VOLTAGE ON THE GENNYS ARM POST !!!!
Is the genny well grounded ????????
Is it properly polarized ????????
John T
Charging Troubleshooting
the gennys FLD post that by passes the light switches Low High control (provides
resistive or direct path to ground IF SWITCH IS WELL GROUNDED) and calls for max
charge and there should definitely be open unloaded voltage on the ARM post way above
7 volts. With FLD post grounded and at fast RPM with no wires on the ARM post what
voltage are you getting ?????? If its good there next the Cutout Relay has to latch
closed (IT needs a good ground to work) so the battery can get a charge. Its hard to
believe theres not high voltage on the ARM with nothing attached if it passes BOTH
motor tests ??????? The light switch can be bad or not well grounded or the cutout
relay may be bad or not well grounded or its not wired right, BUT YOU GOTTA GET HIGH
VOLTAGE ON THE GENNYS ARM POST !!!!
Is the genny well grounded ????????
Is it properly polarized ????????
John T
Charging Troubleshooting
Field grounded, no load Voltage on Armature was 0 volts with both a digital and analog voltmeter.
Both motor tests passed with no doubts.
Generator is mounted and grounded well. Will check that again but we moved it to take the belt off and and back, hard to believe the ground is that intermittent.
We polarized the generator many times throughout our troubleshooting.
Thanks John T!
Aircraft800
New User
Any luck fixing your generator issue? I have a 1950 MT that shows no amps in low or high charge, but negative with lights on, so I know I have a charging problem. I just started doing research and found your thread. I'll start ringing out wires and follow John T's guide (His other guide is great too, fixed my ignition problem), just curious what you found.
how are the brushes? i`ve had use my finger to reach the brushes and see if they are stuck, have free pressure to the armature,and see if there are sparks(needs to be dark) when gen is running. also the grooves on the armature could maybe need cleaning where brushes ride.
Aircraft800
New User
Thanks!! I found the problem rather quickly using John T guide. I had no power at the field or armature, polarized the armature by momentarily jumping the starter switch terminal to the ARM terminal on the Generator, I heard the cutout click and a small spark, everything is back to normal!
Watthour
Member
Glad you got it. I found the same thing on an M, an MT, an LA, an H, a couple Bs, and host of others that hadn't run for 20-ish years where the iron had just lost residual magnetism and needed to be "reminded" once they were started. I was afraid to straight-on jumper them to a battery so I used a 50W 10Ω wirewound resistor and slowly let the windings saturate and build some decent magnetism before cutting them loose. The effect is the same, and once they start making current the same thing will happen naturally, but I had no idea of the condition of the units after a couple decades of rest.
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