How to check a generator

I have 2 Oliver 550's, one runs and the other has the motor tore down. I loaned the runner to my old boss to plow his driveway this winter. I was over there last week putting chains on it, started and shut it off several times and then the battery was dead. Jumped it to get it started and it wasn't charging. The P/O had wired a amp guage into the system and when I was using it last summer, the guage worked like it should. I took the generator for the other one over and put it on today and it doesn't charge either. I had a test light with me and tried touching both posts on the generator and got nothing. I have an 88 with a generator and when running, one of the posts will light the test light. I got nothing out of either of these generators. Is there any way I can check a generator to see if it's putting out any charge? I tried the John Deere dealer, the battery shop, 3 parts stores and no one local can test a generator. Now What do I do?? Chris

If I remember correctly with the engine running you should ground the F terminal and it should go full charge. there is wiring schematics out there on YT also to make sure the wiring is hooked up right. I have switched over to alternator as they are simpler ti fix and have more amps to us if 12 volts.

Pictures from my phone. Both terminals on the guage will light the test light. The small white wire to the regulator will light that terminal on the regulator. I didn?t have a small enough screw driver to take the cover off of the regulator.

With it running ground the field terminal on the generator, it will have a F stamped beside it. If it charges, the generator is good, if not it's the regulator or wiring.

The generator is likely a Delco A circuit generator. The simple test is to start the tractor and use a jumper wire to ground the F terminal on the generator. this causes it to put out full power, which is OK for a modest time like a minute or so. The amp meter should show a nice charge rate. If it does, I would replace the regulator. Find a good USA made Delco regulator, not cheap import. If it does not charge, it could be the generator or the cutout relay in the VR. Use the link to get more serious. Jim
VR
The VR relay (of the two in the housing) is normally directly grounded through closed points. There may be 2 sets of contacts on that relay, but the one that stays closed when the engine is off (the upper one), is the active set. Thus when the VR is grounded to the tractor engine (it must be for it to work, check for a perfect ground to the regulator frame) the contacts ground the field circuit. When the voltage is higher than intended (by the settings of the gaps and spring tension) the contacts open and let the ground circuit flow through a resistor to lower the charge voltage. The process is random and pulsed DC control. Very electronically noisy. But the average current causes the average voltage to be correctish. If yours works when the field is jumped to ground, your regulator is not putting the connection through the points to ground (as it should). It is not likely the points, it is likely the regulator ground. Jim
? Read up here http://www.navioneer.org/riprelay/The%20Navion%20Files/Delco_Remy_Generator_Regulators.pdf
John T analysis chart.

First has your battery been disconnected from the generator or been run down to a low charge?
If this has happened you will need to polarize (calibrate) the newly charged battery to the generator/regulator. this is done by using a wire to arc the ground to the "F" (Field) terminal. Arcing only takes a spark. Also generators charge at a higher RPM whereas alternators can charge at an idle.

(quoted from post at 22:46:11 01/09/20) First has your battery been disconnected from the generator or been run down to a low charge?
If this has happened you will need to polarize (calibrate) the newly charged battery to the generator/regulator. this is done by using a wire to arc the ground to the "F" (Field) terminal. Arcing only takes a spark. Also generators charge at a higher RPM whereas alternators can charge at an idle.

Click to expand...

" has your battery been disconnected from the generator or been run down to a low charge?
If this has happened you will need to polarize (calibrate) the newly charged battery to the generator/regulator. this is done by using a wire to arc the ground to the "F" (Field) terminal"

Fatamus, sadly, there's not a single part of your post that is true.

A generator that has been functioning is unaffected polarity-wise by a low or disconnected battery.

Although it never hurts (if done carefully and correctly) to polarize a generator.

The consensus is that the O.P.'s charging system is a Delco (which is an "A" circuit charging system).

To polarize an "A" circuit charging system, momentarily jumper the "BATT" and "ARM" terminals at the voltage regulator (for convenience), or momentarily jumper the ungrounded battery terminal to the "A" (ARM) post on the generator.

You ask " Is there any way I can check a generator to see if it's putting out any charge"

ANSWER YESSSSSSSSSSSS (see below including Genny Motor test)

Before guessing or throwing parts at it, to determine the cause of non charging and to see if its a Class A system Generator orrrrrrrrr a Voltage Regulator and ways to test (see my Generator Motor Test paragraph) issue work through my Troubleshooting Procedure and it can help find the problem.

Don't forget BOTH the Genny and VR need good grounds and to be safe Polarize the genny BEFORE start up.


https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=ttalk&th=2060825

John T
John Ts Charging Troubleshooting