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STARTING SYSTEM FAULTS AND THEIR SYSTEMATIC LOCATION
Indications of Trouble in Gray & Davis Systems—Faults in Motors and
Generators—Commutator Faults—Fitting Brushes—Faults in WiringCare of Lamps and Storage Battery—Delco System Troubles—Testing for Defective Windings—Defects in Dyneto Systems—Troubles in BoschRushmore System-Remy System Faults.
This portion of the treatise is intended primarily for the mechanic who may be confronted with more or less complex problems in caring for and repairing the electrical system, though the instructions given are sufficiently complete and so simply expressed that the motorist can avail himself of them. The mechanic who has had experience on electrical apparatus has invented methods whereby he checks or tests various parts of the apparatus, but quite often these checks or tests are not infallible. It is the aim of this chapter to point out to the mechanic the most practical manner of making reliable tests. The importance of searching for trouble in a systematic manner cannot be too strongly emphasized. The expert always follows a definite course of procedure in locating derangements, the amateur works in a haphazard manner and seldom accomplishes anything. One finds trouble by a process of search and elimination, the other finds it by good fortune if the fates are kind.
Locating Troubles in Gray & Davis System.-In event of trouble with the Gray & Davis lighting system, the makers recommend a careful study of the symptoms, which will usually provide a guide to find the component at fault. The indicator on the dash shows positively any failure of the generator or any break in the wiring. If the indicator does not indicate "charge” when the engine is speeded up but shows “discharge” when lights are turned on and the engine at rest, the dynamo or current regulator is not
working properly. A common trouble is the dynamo brushes not sliding freely in their holders. If the dynamo is driven by friction belt this may be too loose to drive the dynamo at proper speed. If the indicator does not indicate “charge” with the engine speeded up and does not indicate “discharge with the lights on and the engine at rest, one should look for an open circuit or loose connection in the battery wiring or for corrosion or looseness in the
storage battery terminals. Sometimes the dynamo terminals may have loosened and imperfect contact exist at this point. Should the indicator show “discharge” with the lights turned off and engine at rest (providing that the indicator pointer is not bent), the insulation on lamp wires may be injured, this permitting contact with the frame, causing a short circuit. If the indicator indicates “charge” with the engine at rest, it is a positive indication that the pointer is bent.
If the charge indications are below normal with the engine running, it may be on account of slipping of the driving belt if the dynamo is driven in that manner, or because of poor adjustment of the centrifugal governor, if that type of dynamo is used. If the ammeter “discharge” inaications are above normal it is a sign that the lamp load is excessive or one of the lamp wires is in contact with the frame. When the indicator pointer jerks from one reading to another with engine running at constant speed on the discharge scale, it means either a short circuit in the system or a loose terminal. If trouble is experienced from fuses burning out repeatedly, it is a sign that the lamp wires are in contact with the frame at some point or that one of the lamps is defective because of a short circuited filament. If the engine cranking speed is very low and this is not due to the engine being stiff, such as would be the case in cold weather or after the engine has been overhauled and bearings tightened, it may be considered a positive indication that the storage battery is almost discharged or that it is defective in some way. If the starting motor does not rotate; the battery may be discharged, the starting switch may not be making good contact or a motor brush may not make good contact with the commutator. There may be an open circuit in the battery wiring to the motor, or there may be a poor circuit or contact because of corroded battery terminals. If the starting motor rotates but does not crank the engine, it is a sign that the overrunning clutch does not work properly or that the starter pinion is not properly meshed with the flywheel gear.
If the lamps will not light but the starter cranks the engine, this shows that the storage battery is in proper condition and that the trouble is due to burned out or broken lamp filament or defective lamp fuses. If the lamps burn brightly but fail to illuminate the road sufficiently, the bulbs may be out of focus in respect to the parabolic reflector of the lamp or the lamp supports may be bent in such a way that the rays of light may be directed too far upwards. If the lamps burn dimly or not at all and it is difficult to crank the engine with the starting motor, this means a weak or discharged storage battery. In addition to this, the lamps may be old and have blackened insides, the system might be slightly short
circuited, or considerable resistance may be present, due to loose or dirty connections. If the lamps blacken or burn out quickly they are not of the proper quality if they are six volt lamps, and not of the proper voltage if other than six volt lamps. There is one exception to this rule, and that is the bulbs of the tail lamp and dash light, which are three volt lamps when these two are wired together in series. Burning out of the lamps may be caused by the regulator not working properly, and if this is the case the lamps will burn out at high engine speed. If the lamps flicker and the ammeter or indicator needle is unsteady, look for loose connections in the light wires, loose connections between battery and dynamo, loose contact at a lamp connector or lamp bulb, poor contact between fuses and fuse clips, or an exposed wire touching the frame intermittently.
If one suspects that the battery is discharged, its condition may be readily determined by using the test lamp, shown at C, Fig. 201. The test lamp may also be used for locating short circuits or open circuits. It is well to bear in mind that the lead terminals of the battery should be scraped clean and bright at the point where the test lamp wires bear in order to insure a good clean contact. If the test lamp burns brightly it shows that there is current in the storage battery. To locate a short circuit the fuses are removed from the rear of the switch and the wire is disconnected from the negative battery terminal. Connect one of the test lamp terminals to the free battery terminal and touch the other test lamp wire to the frame of the car. The test lamp should light if good contact is made, this indicating that the positive battery terminal is properly connected to the ground. Keep one test lamp wire in contact with the negative terminal and touch the other wire to the end of the battery wire just disconnected. If the test lamp lights it shows that a conductor or wire connected to the battery, lamps, horn or starting motor is in contact with or grounded to the frame of the car.
Any wires having injured insulation should be wrapped with electrical tape to prevent metallic contact between the conductor and the frame. Open circuits are best indicated by feeling of the wires where they fasten to the terminals to make sure that posi
tive contact is made and that the terminal binding nuts are not loose. Short circuits may also be located if no test lamp is available by following the various wires, and if any of these are found in contact with the frame it is a wise precaution to pull them away and to wrap the section that was in contact with the frame thoroughly with insulating tape. If one lamp flickers and the rest burn brightly, look for a poor connection between the lamp and the lamp connector, a loose terminal at the junction switch or a defective fuse. If all lamps flicker, look for loose connections in wiring between battery and junction switch. When lamp bulbs have been renewed in head lights it is sometimes necessary to refocus the lamps. Head lights should not exceed 15 candle power, and should always be of the high efficiency filament type. Cheap carbon filament lamps will not only consume undue current but will not prove enduring. Tungsten filament lamps are best.
Faults in Motors and Generators.—While every effort has been made by the manufacturers of electric starting and lighting systems to have the various units function as nearly automatically as possible, it will be evident that some attention will be needed by the various units. The generator should be looked over from time to time and should any carbon dust be worn from the brushes by the commutator and deposited in the lower part of the casing it should be blown out with compressed air. It is stated that an accumulation of this dust may result in a ground to the generator case or produce a short circuit between the brush carrier and case. If the commutator is blackened or rough it must be smoothed down with fine sandpaper while the armature is rotating.
Never use emery cloth for this purpose. After smoothing down the commutator remove all particles of metal which may bridge across between the copper segments. The insulating material between the commutator segments should not be higher than the surfaces of the segment, and if any of it projects it must be filed down slightly lower than the copper pieces by using a small file as shown at Fig. 264.
The brushes are the part of the generator that demand the most attention and to which most of the troubles in devices of this kind are due. They should be examined to see that they are in perfect