Putnam's Automobile Handbook: The Care and Management of the Modern Motor-Car

by H. Clifford Brokaw; Charles A. Starr

The next step would be to test where the wire leaves the switch to go to the device to be operated. If the current gets to the switch and does not get out of it, it is apparent that the trouble is in the switch, or if it gets to the switch but not through the fuse, the fuse is at fault.

If the current leaves the fuse and does not get to the lamp which the switch controls, then we know that the trouble is in that wire somewhere; if it gets to the lamp but the lamp will not light, we know it is in the lamp; if we can trace it through the lamp, but it does not reach the battery, we know that it is the wire leading back to the battery which is at fault.

If the current is carried back through the frame of the car, as is very often the case, frequently the ground connections are poor or there is a break in the ground. Thus, we might attach a ground wire to a piece of iron on the dash, and if this is of wood that piece of iron might be insulated from the remainder of the metal work of the car and the ground connection would not be complete.

Recently the author came across some electrical troubles which were rather mysterious to the owners of the cars, but proved to be simple under systematic search. One man worked all of one Sunday morning, with the help of several sympathetic owner friends trying to find out where an extra wire on his switch should be connected. He could not get the engine started, the horn would not blow, the headlights would not light, the starting motor would not turn over, but the dash and tail lights, which were in series, did light.

A little experiment developed the fact that when the starting pedal was depressed the dash light grew very dim. This, of course, indicated that it was not possible to draw a very large amount of current from the battery, or that the battery was either in a discharged condition, or that the connections leading from it were poor. It was found that when the wire connected to the battery terminal was moved, the light would brighten up. This wire was disconnected and cleaned carefully to make sure that the contact was good. When it was assembled again no improvement was shown, so it was taken apart again and a careful inspection showed that one end of the taper on the inside of the terminal had a slight shoulder, which prevented the taper end of the wire from being drawn into place snugly. Therefore a very light contact was made and sufficient current could not pass to operate the starting motor. This shoulder was removed with a penknife and the engine started without difficulty. Several hours’ time would have been saved if the owner had started to look for the trouble at the source of the current instead of puzzling over the end of a wire that was not intended to be connected to anything and had nothing to do with the trouble. It was simply an extra wire for use if some new device should be installed.

A week later this same man was unable to start his engine and again worked over it several hours before calling for help. This time the lights were all right, but the engine would not start. To determine the condition of the battery, he turned on a light and depressed the starter pedal as before, to see if the light would dim very much under the heavy load; as it did not, it was decided that the battery was all right this time.

The hood was open and it was observed that when the starter pedal was depressed the fan did not revolve and therefore the engine was not being turned over, though one could hear the starting motor buzzing plainly. This showed that the overrunning clutch of the starting motor was slipping. As correcting this trouble was a shop job, they cranked the engine over by hand, but still it did not start.

To make sure that a spark was being delivered, the wire leading from the ignition coil to the high tension distributor was disconnected and given about ¹⁄₁₆ inch gap. As soon as this was done it was plain to see that a spark was being delivered, and the engine started immediately also. Making a slight gap in the secondary circuit increases the intensity of the spark at the plug and often aids in starting a balky motor. This was an occasion when an outside spark gap was of value. After the engine was warmed up, it was started several times without difficulty.

Another fellow who was in trouble had a “sick” horn. It sounded like a man who has a cold clogging his vocal organs—that is, it gave a cracking or rattling sound instead of a musical note, if the sound of a horn can be called musical. This type of horn has a notched wheel which revolves and strikes against an iron pin riveted into a disc. The disc in this way is made to vibrate, giving the desired sound. An examination showed that the pin had become loose and rattled. It was explained to the owner what the trouble was and he was told that the pin was of hardened steel and as it was rather difficult to rivet it, it might loosen up again. He replied that he would not worry about that, because now that he knew what the trouble was he could easily get it fixed again or replace it if necessary.

Another fellow had a horn which would not play because it had become grounded and blown the fuse. The ground was removed, but as no fuse could be obtained, a single strand of very fine wire from an ignition cable was substituted in place of the fuse. This wire was small enough to burn up before other short circuits could do damage to battery or wiring.