Re: Ammeter

Posted by HH56 On 2024/5/22 18:38:20

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.