The generator troubles which are most likely to exist are:
a. Dirty commutator.
b. Dirty brush contact surface.
c. Loose brushes.
d. Brushes bearing on wrong point of commutator (to set brushes properly, remove all outside connections from generator, open the shunt field circuit, and apply a battery across the main brushes. Shift the brushes until the armature does not tend to rotate in either direction. This is, of course, a test which must be made with the generator on the test bench).
e. Loose connections in the shunt field circuit.
The foregoing conditions are the ones which will generally be found. More serious troubles will generally prevent the generator from building up at all.
2. Cutout does hot open when engine stops. This condition is shown by a discharge current of about 5 amperes when the engine has stopped. (In Delco systems which have no cutout, an even greater discharge will be noted as long as the ignition switch remains closed.) This trouble is generally due to cutout points stuck together, a broken cutout spring, or a bent or binding cutout armature.
3. Cutout does not open until ammeter indicates a discharge of three or more amperes (in addition to the ignition discharge). This may be remedied by increasing the spring tension of the cutout, or removing any trouble which causes the cutout armature to bind. On many cutouts the armature does not actually touch the core of the cutout winding when the points are closed, there being a small piece of copper or other non-magnetic metal on the armature which touches the end of the cutout and maintains a small air gap between the core and armature, even when the points are closed. The opening action of the cutout may be changed by filing this piece of non-magnetic material so as to decrease the air gap, or pinching it with heavy pliers so as to make it stand farther out from the cutout armature and thus increase the air gap between the armature and core when the points are closed.
Decreasing this air gap will cause the cutout to open late, and increasing it will cause the cutout to open early.