From: https://www.pilotsofamerica.com/communi ... or.117998/
1. Funny you should ask, we just had a whole thread on this. As luck would have it, I just went through this exercise with my tractor Genny. First, check that the generator is in good repair. You can do this easily a couple of ways; pull off the belt and apply 12v + to the arm and - to the field. If it "motors", that is turns (it'll be slow), the brushes, field and arm are good. Then, the belt back on and jump the arm and field. Put a voltmeter from the arm to ground and start the motor at slow idle. If you have voltage that increases with engine speed the Genny is good. Be careful! Voltage can get pretty high in a short time, don't go much over high idle. Mine cranked up to 40v in the blink of an eye. Survived it though.
You can fart around with trying to adjust regulator voltage and cutout, but it can be tough to get right without an external variable power supply. Start with cleaning and adjusting the contact points with a points file. You don't need to remove the pits, just the oxidation. I took a feeler guage and took measurements before I started to get them reset ball park after cleaning. It's '30's tech, ball park is good enough. After you reinstall it, be sure the cutout ( the bobbin with the big wires) remains open until the Genny starts to produce, then it should close. Don't close it manually, the contacts can short together and you'll not get them open again. Charging output should be 13.5 -14.25 volts, but give the regulator a chance to warm up before you'll get a reliable reading. Put the cover back on, it makes a difference.
You can adjust output voltage by opening and closing the voltage bobbin gap (the one with the littlest wires). Cutout and current can be adjusted as well, but I found resetting to pre-cleaning gaps was fine.
Of course, don't neglect simple wiring and terminal corrosion issues, and check that he regulator itself has a good ground
2. Disconnect both wires from the generator.
Place a ammeter from the (A) post to ground
Place a wire from the battery (+) to the (F) momentarily
The Ampmeter should show a momentary output while voltage is applied to the (F)
When no amperage out put, you have an open field circuit.
probably bad brushes.
I should add, the engine must be running when you do this test.
3. Another check - Look at the wire wound resistor(s - I think there are normally two) underneath the voltage regulator. If any are open, it's time for a new regulator. These resistor(s) are the 1930 version of a flyback diode. If any resistors are open, the regulator points will quickly fry themselves with the inductive kick if the regulator vibrator operation into the inductance of the field coil.
4. You can test the continuity of the armature by seeking continuity from segments 180 degrees apart. more than any 2 segments and it is a shorted armature.
5.
From: http://www.bowersflybaby.com/tech/spark2.html
1. The procedure:
1. Ensure the power is turned off to all electrical devices in the aircraft. Remove the fuses or trip the circuit breakers, if convenient In fact, my advice is to disconnect them entirely (see below).
2. Turn off the main power switch (master switch)
3. Disconnect the wire that goes to the "GEN" terminal (sometimes marked "ARM") and connect it to the "BAT" Terminal (sometimes marked "Battery" or "12V").
4. Disconnect the wire on the "Field" terminal (May be marked just "F" or "FLD") on the regulator and connect the wire directly to ground.
5. As of this point, the "GEN" and "Field" terminals of the regulator should have nothing connected to them.
6. Make sure the wheels are chocked.
7. Get in the airplane and remove the fuse/pull the circuit breaker that controls current to the generator.
8. Turn on the master switch.
9. Verify, again, that all power is off to the aircraft electronics.
10. Start the engine
11. Enable the generator (turn the second half of the split master on, insert fuse, push circuit breaker in, etc.).
12. Watch the voltmeter. With the engine idling, the voltmeter will probably be reading less than 12 V.
13. Slowly increase the engine speed while watching the voltmeter
14. When you get to about runup speed (1800 RPM), the voltmeter should be reading about 12V
15. As the RPM increases, the voltage should also increase. Try not to let the voltage rise above ~14.5 volts.
16. Kill the generator power and shut down the engine
So: If the voltage DID rise with RPM, your generator is functioning. If it got above 14 volts, it's probably fine and the problem lies in your regulator. The strange thing is, if you download those Delco-Remy Regulator Service Manuals, they give instructions on how to service and adjust the regulators. I'd really recommend just a replacement, though.
If the voltage didn't come up, then your generator is bad. Removing the generator isn't too hard, but you'll have to remove the left magneto to get at the top nut. You can often get these generators rebuilt at local auto electrical shops, but many will not touch aircraft generators for legal reasons. Don't volunteer that it came from a plane... just ask if they can check out an old generator and rebuild it if necessary.
From: https://www.jalopyjournal.com/forum/thr ... lp.269801/
1. Saturday night the amp gauge stopped showing any charge so I went home while I still could. Took the short and easy route and bought a new regulator which didn't help at all.
After reading up on how these work I found a few tests that could be done to verify their function
a) Disconnect the v-belt and wires, run power to the armature post and ground the field post. The generator should now spin and act as a motor, disrupting the field/ground circuit should make the speed go up. Mine spins like a motor but if there is a speed increase it's very very small.
b) Disconnect all wires, run the engine. Connect a voltage gauge across Armature and ground and then ground the Field post.
Voltage should now be linear to the engine speed and show up to 40 volts. Mine shows nothing.
Measuring the resistance across the field coils shows abt 10 ohms and measuring the coils on some spare housings shows abt the same resistance.
From: somewhere else
1. Simply put a clamp-on ammeter around pos. battery cable or wire in a amp guage between cable and battery, after tractor is running though!!!! Then simply hook a jumper wire from field terminal of generator to ground and read amperage. Only do this for a very few seconds!!! If all of a sudden you read amperage then regulator must be faulty. If you still read nothing then get starter/generator tested at rebuild shop
From: https://p15-d24.com/topic/39465-generat ... -grounded/
Generators are classified as Type A or Type B.
For Type A generators, the field current (and thus the output voltage) is controlled by rapidly vibrating (opening and closing) voltage regulator contacts inside the voltage regulator. These vibrating contacts provide intermittent grounding for the field windings. Because these contacts provide ground for the field windings from outside the generator itself, this type of generator is called an external ground (Type-A) generator.
For Type-B generators, the field current is also provided by rapidly vibrating contacts inside the voltage regulator, but in this case, these contacts do not provide ground. Instead, they sample the generator output. The field windings are grounded inside the generator so this type of generator is referred to as an internal ground (Type-B) generator.
Type A - External Ground Type B - Internal Ground
The diagram below comes from the 1951 Dodge Truck Shop Manual on page 208. The generator ( labeled #12) in the diagram matches Circuit A above. So, the generators in Pilothouse Trucks are Externally Grounded.
How to Polarize a Pilothouse Generator
To polarize an "A" circuit generator (external ground), momentarily connect a jumper lead between the regulator BATTERY and ARMATURE terminals after all leads have been connected, but before the engine is started. (This is how a Pilothouse Generator should be polarized!)
To polarize an "B" circuit generator (internal ground), disconnect the lead from the regulator FIELD terminal, and momentarily touch the lead to the regulator BATTERY terminal. This should be done after all other leads have been connected and before the engine is started. (Pilothouse Trucks are not polarized this way!)
A Goes With A and B Goes With B
Another thing to remember is that generators AND voltage regulators are classified as either Type-A or Type-B. They must match. If you have a Type-A generator, then you must use a Type-A regulator. Type-B regulators are only for Type-B generators also.
A Way to Check Whether a Generator is Type-A or Type-B...
I wanted to prove for my own satisfaction that my B3B generator is externally grounded (Type-A). So, using the Type A and Type B diagrams above as guides, I measured the resistance between terminals A and F and compared it to the resistance measured between F and ground (which I call G) on the generator case. Here's how I decided if my generator is Type-A or Type-B:
If the generator is externally grounded (Type A), then the resistance measured between terminals A and F should be less than the resistance from F to ground (the generator case).
If the generator is internally grounded (Type B), then the resistance measured between terminals A and F should be greater than the resistance from F to ground (the generator case).
Why should this test work? Because for Circuit A (External Ground) the ohmmeter current from A to F only goes through the field windings, whereas current from F to G goes through the field windings AND the armature windings. The reverse is true for Type-B).
For my generator, (A to F) was 3.6 Ohms and (F to G) was 3.9 Ohms which tells me that my generator is externally grounded which agrees with the diagram from the Dodge shop manual.
(Information above was taken from http://www.bowersflybaby.com/tech/delco ... erator.pdf and the Dodge B-3 Shop Manual.)
Generators are classified as Type A or Type B.
For Type A generators, the field current (and thus the output voltage) is controlled by rapidly vibrating (opening and closing) voltage regulator contacts inside the voltage regulator. These vibrating contacts provide intermittent grounding for the field windings. Because these contacts provide ground for the field windings from outside the generator itself, this type of generator is called an external ground (Type-A) generator.
For Type-B generators, the field current is also provided by rapidly vibrating contacts inside the voltage regulator, but in this case, these contacts do not provide ground. Instead, they sample the generator output. The field windings are grounded inside the generator so this type of generator is referred to as an internal ground (Type-B) generator.
Type A - External Ground Type B - Internal Ground
The diagram below comes from the 1951 Dodge Truck Shop Manual on page 208. The generator ( labeled #12) in the diagram matches Circuit A above. So, the generators in Pilothouse Trucks are Externally Grounded.
How to Polarize a Pilothouse Generator
To polarize an "A" circuit generator (external ground), momentarily connect a jumper lead between the regulator BATTERY and ARMATURE terminals after all leads have been connected, but before the engine is started. (This is how a Pilothouse Generator should be polarized!)
To polarize an "B" circuit generator (internal ground), disconnect the lead from the regulator FIELD terminal, and momentarily touch the lead to the regulator BATTERY terminal. This should be done after all other leads have been connected and before the engine is started. (Pilothouse Trucks are not polarized this way!)
A Goes With A and B Goes With B
Another thing to remember is that generators AND voltage regulators are classified as either Type-A or Type-B. They must match. If you have a Type-A generator, then you must use a Type-A regulator. Type-B regulators are only for Type-B generators also.
A Way to Check Whether a Generator is Type-A or Type-B...
I wanted to prove for my own satisfaction that my B3B generator is externally grounded (Type-A). So, using the Type A and Type B diagrams above as guides, I measured the resistance between terminals A and F and compared it to the resistance measured between F and ground (which I call G) on the generator case. Here's how I decided if my generator is Type-A or Type-B:
If the generator is externally grounded (Type A), then the resistance measured between terminals A and F should be less than the resistance from F to ground (the generator case).
If the generator is internally grounded (Type B), then the resistance measured between terminals A and F should be greater than the resistance from F to ground (the generator case).
Why should this test work? Because for Circuit A (External Ground) the ohmmeter current from A to F only goes through the field windings, whereas current from F to G goes through the field windings AND the armature windings. The reverse is true for Type-B).
For my generator, (A to F) was 3.6 Ohms and (F to G) was 3.9 Ohms which tells me that my generator is externally grounded which agrees with the diagram from the Dodge shop manual.
(Information above was taken from http://www.bowersflybaby.com/tech/delco ... erator.pdf and the Dodge B-3 Shop Manual.)
Electric diagram of an early Case 444 with the generator warning light