cut out relay testing/questions

You can try bending the moveable contact to increase the air gap and see if that will let it open with no generator voltage--i.e. less than 6.5 volts.

If it will open that way and still close at 6.5 volts your luck is better than mine. I have heard about folks adjusting relays and voltage regulators and the FO 4 suggests it can be done but I have never had any luck with anything short of replacing them.

YOur mileage may vary

Ed in Ill? (check archives) finally got PO'd and bitt the bullett and got a real solid state stealth VOLTAGE REGULATOR from "Fun Projects" company. Its built into a roundcan just like your infamous cut-out relay. It is more than just a "diode" and actually gets rid of fiddleing with your 3rd brush too. It is also popular with Model T guys..... .....Dell

• 2N voltage regulator

Arc-spark your 2-terminal roundcan cut-out relay while your relay is GROUNDED. This magnetizes the relay core to be REPULSED by the electro-magnetic field caused by your BATT terminal when the genny stops gennin'. This REPULSION is what causes the cut-out relay to UNLATCH when the genny nolonger outputs charge into the battery.

Everytime you MANUALLY close your cut-out relay with BATT volts on BATT terminal, you re-polarize your cut-out relay core the WRONG polarity.

As you noted when your battery acts as a substitute genny, the cut-out relay closes pushing charge INTO the battery. When the genny STOPS charging the battery, the stored electrons come outta the battery, thru the finewire coil to ground. The finewire coil has a magnetic field that is OPPOSITE to the IRON CORE magnetic (as set by "polarization") field and causes the magnetic attraction to the relay armature to weaken so that the relay spring pulls the relay contacts APART. And therefore your cut-out relay disconnects your BATT terminal from the ARM terminal and stops the battery from discharging thru the generator gutts..... .....HTH, Dell

The results you are getting are normal. There is a winding from the GEN terminal to ground. When you hook the battery to the BATT side, and close the contacts, you are backfeeding the GEN side from the battery side, and with this current flow to the GEN side, and then through the windings to chassis ground, the electromagnet remains energized, and will not drop out the contacts.

The secret to how this system works is as follows.
When you start the tractor with a functioning generator, as the engine speed comes up, and the generator begins to charge, the voltage to the GEN side of the cutout causes the cutout to pull in, allowing the output of the generator to charge the battery. There is another, heavy, winding in the cutout that is placed in series between the generator and the battery when the points are closed. When the engine speed drops below the speed needed for the gnerator to produce a voltage greater than the battery voltage, there is a reversal of current flow through the heavy windings in the cutout. This causes the magnetic field produced by the electromagnet to drop to zero for in instant before reversing. It is in this instant that the cutout points must open, or they will remain held closed by the magnetic field produced by the now-reversed current flow FROM the battery TO the generator.

A CUTOUT WILL NOT DROP OUT UNLESS THERE IS THIS REVERSAL OF CURRENT FLOW AS THE GENERATOR CEASES CHARGING, AND ACTUALLY BEGINS TO DISCHARGE. When you are "testing" the cutout as you describe, this phenomenon is missing, and the points will remain closed untill the battery is dead enough there is no longer enough magnetism to overcome spring tension, and the points open.

There is more to a cutout than a simple relay, as most people seem to think of them. You may just have a bad cutout, as many of the curent crop of cheap imports seem to be. The setting of spring tension and air gap work together to determine at what generator voltage the cutout will pull in. A properly functioning generator also helps everything to behave as it should!

• Ford cutout schematic