Troubles
The operation of the electrical system when the engine is running may not be as described in the foregoing paragraphs. Troubles may be found as follows:
1. Cutout does not close until engine reaches a speed in excess of 10 miles per hour. This trouble may be due to the cutout or to the generator. If the ammeter shows a charging current of three amperes or more as soon as it closes, the cutout is at fault. The thing to do in such a case is to adjust the cutout. First see that the movable armature of the cutout moves freely and does not bind at the pivot. If no trouble is found here, the thing to do is to decrease the air gap which exists between the stationary and movable cutout points when the cutout is open., or to decrease the tension of the spring which tends to keep the points open. On most cutouts there is a stop which the cutout armature strikes when the cutout opens. By bending this stop the air-gap between the points may be decreased. This is the adjustment which should be made to have the cutout close earlier, rather than to decrease the spring tension. Some cutouts have a spiral spring attached to the cutout armature. Others have a flat spring. On still others, the spring forms the connection between the armature and the cutout frame. In the first two types, the spring tension may be decreased, but wherever possible the air-gap adjustment should be made as described.
If the cutout closes late, and only about an ampere of charging current is indicated on the ammeter, and the cutout points are fairly clean and smooth, the trouble is generally in the generator.
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.
4. Cutout will not close at any engine speed. If cutout does not close the first time the engine speed is increased, stop the engine. This condition may be due to a defective cutout, an open-circuit in the charging line, a ground or short-circuit between the cutout and the generator, or a defective generator. To determine whether the cutout is defective, remove the wires from it and hold together the ends of the wires coming from the generator, and the one going to the ammeter. Start the engine. If no other trouble exists, the ammeter will indicate a charging current at speeds above 8-10 miles per hour. If no current is obtained, stop the engine. If the cutout trouble consisted of an open circuit in one of its windings, or in the points not closing, due to dirt or a binding armature, or if there is an open-circuit in the charging line, the generator will, of course, have been running on open-circuit. This will cause the fuse in the shunt field circuit to blow if there is such a fuse, and if there is no such fuse, the shunt field coils may be burned open, or the insulation on the field coil wires may have become overheated to a point at which it burns and carbonizes, and causes a short-circuit between wires. Such troubles will, of course, prevent a generator from building up when the cutout wires are disconnected and their ends held together.
If there is a ground in the cutout, or between the cutout and the generator, the generator will very likely be unable to generate (if a “one-wire” system is used on the car). If there is some defect in the generator-such as dirty commutator, high mica, brushes not touching, commutator dirty, or loose brushes, brushes too far from neutral, grounded brushes, brushes not well ground in, wrong type of brushes, grounded commutator or armature windings, short-circuited commutator or armature windings, open-circuited armature windings, grounded field windings, short-circuited field windings, open-circuit or poor connections in field circuit, one or more field coil connections reversed, wrong type of armature or field coils used in repairing generator, generator drive mechanism broken-then the generator will not build up.
If no charging current is, therefore, obtained when the generator and ammeter wires are disconnected from the cutout and their ends held together, there may be a ground or short-circuit in the cutout windings or in the circuit between the generator and the cutout, or the generator may be defective, due to having been operated on open-circuit, or due to troubles as described in the foregoing paragraph. The presence of a ground or short in the circuit between the generator and cutout or in the cutout may be determined by disconnected the wire from the generator, disconnecting the battery (or ammeter) wire from the cutout, and running a separate extra wire from the generator to the wire removed from the cutout. Then start the engine again. If a charging current is obtained, there is a ground or short either in the cutout or in the circuit between the cutout and the generator. (It is also possible that the failure of the generator to build up was due to poor brush contact in the generator. The use of the extra wire connected the generator directly to the battery, thus magnetizing the generator fields and causing generator to build up. If poor brush contact prevented the generator from building up, closing the cutout by hand will often cause the generator to start charging. If you can therefore cause the generator to build up by holding the cutout points closed by hand, or by shorting across from the generator terminal to the battery terminal of the cutout, it is probable that the generator brushes are not making good contact). The cutout may be tested by stopping the engine, replacing the battery (or ammeter) wire on the cutout, and holding the end of the extra wire on the generator terminal of the cutout. If a charging current is then obtained, the cutout is 0. K. and the trouble is between the cutout and the generator.
5. An excessive current is obtained. If a third brush generator is used, look for loose or dirty connections in the charging line, dirty cutout points, dirty commutator, dirty brushes (especially the brush, or brushes, which is Dot connected to one end of the field winding), brushes loose, brushes not well ground in, and any other conditions which will cause a high resistance in the charging line. It is characteristic of third brush generators that their current output increases if there is an increase in resistance in the charging circuit. If no troubles such as those enumerated above are found, the third brush may need adjusting.
Generators using vibrating current or voltage regulators will give an excessive output if the points need adjusting or if the regulating resistance is short-circuited.
Generators using reversed series regulation will give an excessive output if there is a short-circuit in the series field coils.
6. Low charging current is obtained. This may be due to adjustment of the regulating device, to high resistance in the shunt field circuit in case of a third brush generator. In case of generators using other kinds of regulation, loose connections, dirty commutator and brushes, etc., will cause low charging current.
7. Generator charges up to a certain speed and then stops charging. The trouble is caused by some condition which causes the brushes to break contact with the commutator, especially in the case of a “third” brush. High mica, loose brush spring, or a commutator which has been turned down off-center may cause the trouble. This trouble most frequently occurs on cars using third brush motor-generators having a 3 to 1 or more speed ratio between them and the engine. These motor-generators operate at such high speeds that high mica and a commutator which is even slightly off center have a much greater effect than the same conditions would cause in separate generators which operate at much lower speeds. The remedy for this trouble is to keep the mica under-cut, and to be very careful to center the armature in the lathe when taking a cut from the armature. In turning down the commutators of high speed motor-generators, special fittings should be made by means of which the armature may be mounted in its own ball-bearings while the commutator is turned down.