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coil, through the primary winding, to the distributor contacts. This is very plainly shown on the circuit diagram. It is the interrupting of this primary current by the timer contacts together with the action of the condenser which causes a rapid demagnetization of the iron core of the coil that induces the high tension current in the secondary winding. This secondary winding consists of sev.

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Fig. 40.—Simplified Wiring Diagram Showing Action of Delco Ignition

System.

eral thousand turns of very fine copper wire, the different layers of which are well insulated from each other and from the primary winding, one end of which terminates at the high tension terminal about midway on top of the coil. It is from this terminal that the high tension current is conducted to the distributor where it is distributed to the proper cylinders by the rotor shown in Fig. 42.

Ignition Resistance Unit. The ignition resistance unit which is shown in Fig. 41 is for the purpose of obtaining a more nearly

uniform current through the primary winding of the ignition coil at the time the distributor contacts open. It consists of a number of turns of iron wire, the resistance of which is considerably more than the resistance of the primary winding of the ignition coil. If the ignition resistance unit was not in the circuit and the coil was so constructed as to give the proper spark at high speeds, che primary current at low speeds would be several times its normal value with serious results to the timer contacts. This is evident from the fact that the primary current is limited by the resistance

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Fig. 41.–Sectional View Showing Arrangement of Wiring in Delco

Ignition Coil.

of the coil and resistance unit by the impedence of the coil. (Impedence is the choking effect which opposes any alternating or pulsating current magnetizing the iron core.) The impedence increases as the speed of the pulsations increase. At low speeds the resistance of the unit increases, due to the slight increases of current heating the resistance wire.

The Circuit Breaker.—The circuit breaker is. mounted on the combination switch as shown in Fig. 42. This is a protective device which takes the place of a fuse block and fuses. It prevents the discharging of the battery or damage to the switch or wiring

to the lamps, in the event of any of the wires leading to these becoming grounded. As long as the lamps are using the normal amount of current the circuit breaker is not affected. But in the event of any of the wires becoming grounded an abnormally heavy current is conducted through the circuit breaker, thus producing a strong magnetism which attracts the pole piece and opens the con.

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Fig. 42.-Delco Combination Switch with Ammeter and Circuit Breaker

Included.

tacts. This cuts off the flow of current which allows the contacts to close again and the operation is repeated, causing the circuit breaker to pass an intermittent current and give forth a vibrating sound. It requires 25 amperes to start the circuit breaker vibrating, but once vibrating a current of three to five amperes will cause it to continue to operate. In case the circuit breaker vibrates repeatedly, do not attempt to increase the tension of the spring, as

the vibration is an indication of a ground in the system. Remove the ground and the vibration will stop.

The Ammeter.—The ammeter on the right side of the combination switch is to indicate the current that is going to or coming from the storage battery, with the exception of the cranking current. When the engine is not running and current is being used for lights, the ammeter shows the amount of current that is being used and the ammeter hand points to the discharge side, as the current is being discharged from the battery. When the engine is running above generating speeds and no current is being used for lights or horn, the ammeter will show charge. This is the amount of current that is being charged into the battery. If current is being used for lights, ignition and horn in excess of the amount that is being generated, the ammeter will show a discharge as the excess current must be discharged from the battery, but at all ordinary speeds the ammeter will read charge.

Construction of 1916 Delco Ignition Distributor.-It is well anderstood that a rich mixture burns quicker than a lean one. For this reason the engine will stand more advance with a half open throttle than with a wide open throttle, and in order to secure the proper timing of the ignition due to these variations and to retard the spark for starting, idling and carburetor adjusting, the Delco distributor also has a manual control. The automatic feature of this distributor is shown in Fig. 43. With the spark lever set at the running position on the steering wheel (which is nearly all the way down on the quadrant), the automatic feature gives the proper spark for all speeds excepting a wide open throttle at low speeds, at which time the spark lever should be slightly retarded. When the ignition is too far advanced it causes loss of power and a knocking sound within the engine. With too late a spark there is a loss of power (which is usually not noticed excepting by an experienced driver or one very familiar with the car), and heating of the engine and excessive consumption of fuel is the result. The timer contacts shown at D and C (Fig. 43) are two of the most important points of an automobile. Very little attention will keep these in perfect condition. These are of tungsten metal, which is extremely hard and

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requires a very high temperature to melt. Under normal conditions they wear or burn very slightly and will very seldom require attention; but in the event of abnormal voltage, such as would be obtained by run

3 AUTOMATIC ning with the battery

WEIGHTS removed, or with the ignition resistance unit shorted out, or with

DISTRIBUTOR a defective condenser,

CONTACT BREAKER these contacts burn rapidly and in a short

ADVANCE time will cause serious ignition trouble. The car should not be operated with the battery

-K removed.

ROTOR It is a very easy

A matter to check the resistance unit by obsery

AUTOMATIC ing its heating when

F

WEIGHTS the ignition button is out and the contacts in the distributor a re closed. If it is shorted out it will not heat up, Fig. 43.—Showing Construction of 1916 Delco and will cause missing Distributor for Six Cylinder Ignition. Note

Six Lobe Cam. at low speeds. A defective condenser such as will cause contact trouble will cause serious missing of the ignition. Therefore, any one of these troubles is comparatively easy to locate and should be immediately remedied. These contacts should be so adjusted that when the fiber block B is on top of one of the lobes of the cam the contacts are opened the thickness of the gauge on the distributor wrench. Adjust contacts by turning contact screw C and lock with nut N. The contacts should be dressed with fine emery cloth so that they

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