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The voltage should stay the same or rise. Is your generator polarized correctly?

Also post a picture of your regulator if you can (cover off).

Ok..I just got home pic to follow

Still looks fine to me tbh.

When running only the top contacts move the middle and bottom to not open they just stay closed…so I’m not sure if those contacts should be doing anything when idling…I ran a high idle and they still remain closed…?

Referring to the drawing I posted on the previous page, post 27, the way most 3 coil regulators including yours works is when you start the engine the residual magnetism in the generator field poles established when you polarized the generator is enough to enable the generator to produce a voltage but not strong enough to provide much current. The generator output is just enough to energize the cutout relay in the regulator and let it close its contacts. Cutout relay will stay closed as long as the engine is running fast enough for the generator to produce a voltage.

Closing the cutout relay connects the battery to the generator via the ARM (or GEN) wire and because the field coils are also connected to that same wire inside the generator the battery voltage is applied to them as well. The other side of the field coils goes to ground in the regulator thru the current and voltage regulator contacts and resistors.

As soon as the field coils get battery voltage the magnetic field becomes strong so the generator starts to put out maximum current and voltage. The current portion of the regulator is then able to open its contact cutting the direct ground so the field coils only are grounded thru the resistors. The voltage section also is able to energize so that contact is also open and again ground to the field coils is thru a resistor. The resistor value is calculated to lower current flow thru the coils and drop voltage and current output but still be enough for a decent magnetic field to keep a decent current. As long as the generator is running and providing an output both the current and voltage contacts will be vibrating to very rapidly open and close so the field coils are grounded directly or thru the resistor. This will regulate current and voltage to the set specifications. Specs are usually a volt above the battery rating and current as determined by how much the car is requiring but not more than the generator or regulator is designed to provide. Adjustment of either current or voltage is done by delaying or speeding up how fast the contacts can operate by changing the tension on the spring that keeps the contacts open. Some regulators do this by bending a tab to increase or decrease spring tension and others have a small adjustment screw arrangement attached to one end of the spring.

When the engine drops down to slow idle speed often the generator will not be producing enough voltage so the cutout relay can stay closed. Harder to see with an ammeter but on cars wth idiot lights the light will come on steady or will flicker at low engine speeds. That part is entirely normal and as soon as engine speed picks up the light will go out or charging will begin showing on the charge side of ammeter.

Different brand regulators have different physical layouts so I can't tell on yours exactly which contact is the cutout and should stay closed and which of the other two should be vibrating. They should be moving though and if it is dark enough you should be able to see tiny sparks as the contacts open and close. The fact they are not moving and your low volt reading when the field is grounded indicates either the generator is not working or the cutout relay can't or won't close so it can.

Ok thank you for that explanation…the generator was refurbished but I have no idea what was done with it as it came from eBay…the original one was never with car as it had alternator…iI examined the regulator contacts closer last night and the field contacts look much different than arm contacts below it and appear dark…if the regulator is toast , can I still test the generator by grounding the FLD terminal at the regulator or is there a way to test the generator at the generator by another method.. i appreciate the time taken to explain the mechanics…I think I have a pretty good grasp on how it all works now

I learned now that the generator that was purchased on eBay was originally a 1946 Autolite Gdz-4817a but was rebuilt to a 4801f which is correct for my 41… but I don’t know if this could be related to what’s going on…as far as the wrong regulator or type a or b for testing? I have the brillman regulator which replaces the original vrp-4002-c for the 4801f…..

Looks like my generator was originally on a Jeep willy

Howard thanks again for the helpful explanation but just FYI to tell which relays are which, the voltage one uses thin wire and the current uses thick wire. The cutout uses both. In addition, the voltage and current relays are connected in series. So I can see that from top to bottom in his one picture it's cutout, current, voltage. Also a minor note that changing the spring force on the relay changes the amount of force it takes to pull in or out, not really the sampling rate. Since the magnetic force is proportional to the current through or voltage across the relay.

Jimmy you need to test the resistance between the field/arm and field/ground terminals on the generator. You should have higher resistance field to ground than field to arm. This is because the field coil should be connected to the armature internally. But some companies made them connected to ground instead and those used a different type of regulator. I don't remember how Jeep did it.

The armature has very low resistance so be sure that you have a good connection on your meter when doing these tests. If you can't tell, then remove the inspection cover and pull out one of the brushes. This opens the circuit between the arm and ground terminals.

Ok when ohm testing the reading went up to and stayed at 4.0 from field to ground….then went up to and stayed at 3.3 field to arm…that is with engine off and wires disconnected….would this be correct for the regulator I have now ?