FORD VAN POINTERS.
Page 27
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By R. T. Nicholson (Author of "The Book of the Ford ").
WE HAVE SEEN that there arc three sources of electricity on the modern Ford—the magneto, the battery, and the generator. The magneto makes electricity for the ignition (as well as for lighting on non-starter models). The battery makes electricity for starting, lighting; and, if so desired, for ignition. The generator makes electricity for the charging of the battery, magneto current being unsuitable for that purpose.
531.--The Electrical Circuits on a Ford Vehicle.
Each of these three electrical machines has its own circuit or path, although certain parts of certain circuits may be common to two or• more systems. For instance, the generator current travels towards the battery by a yellow wire, which also serves to carry battery current towards the lights. First get a clear notion of three fundamental facts. Assuming that the source of electrical energy is efficient :— (1) The current will get. back to its source if there is a complete path out and home, and only then. Unless there is such a. complete path there will be no current at all in the circuit. This implies (a) That there is a " positive " way out from a terminal. Front door.
(b) That there is a " negative " door home, not always in the form of a terminal. Back door.
(c) That there is a• complete path from the " positive" exit to the "negative ' entrance. (2) An insulated wire is used to carry the current up to the point where such current does the work we ask of it. From that point back to home the current may be carried by any conductor (not usually a wire) that will complete the circuit. Such a "wireless conductor is usually termed "earth," although that term is misleading, inasmuch as the real earth does not enter at all into the circuit in most cases.
(3) The current from any source of electricity will always go home to that source' and to no other, if the circuit is complete—magneto current to magneto,
battery current to battery, and generator current to generator. Regard a source of electrical energy as a lender that insists on getting paid back in its own coin. It will refuse any other. So far as any electrical machine is concerned, its currency is its current, and it will take no other—however good the substitute may be. It insists on " getting Jts own back."
Troubles of the Circuits Classified.
If you. have a clear notion of these three fundamental facts you will see that (assuming the efficiency of the electrical machine itself) all troubles whatsoever arise from failure due to either—
(1) The circuit being broken.
(2) The circuit being a wrong one. If the circuit is broken there will be no external current at all, since electricity will never leave its source unless it has a complete way out, round and back.
If the circuit is a wrong one, the current will get out, round, and back all right, but it will not pass through the point where we want it to work for us : it will get through by some route which is shorter than the route we want it to take—by a " short circuit "—which will almost always be by "earth."
There is just one exception to the first short rule laid down above as to electrical failure being possibly .due to a broken circuit. There is one point at which we get the results we want by deliberately breaking the circuit. 'That one point is the sparking plug gap. In point of fact., however, the gap there is RO small (one thirty-second of an inch is what it should be on the Ford) that it really does not interrupt the eh-
cuit: the electricity jumps the gap, producing a spark, which is precisely what we are after. Except in this one case, a break means a breakdown.
You will note that I have been able to reduce all troubles to two main kinds, assuming the efficiency of the electrical machine concerned. Of course, if the machine is in such a state that it is incapable of output, you cannot get results, however right your circuits are. But the sources of supply rarely fail. Even in their cases' when they do fail, the internal troubles are almost always due to either a break in an internal circuit or to an internal short circuit' • but the "parts concerned" are generally not get-atable, and the attention required often calls for a high order of knowledge and skill, so that cures of such internal troubles are Usually beyond the driver. External circuit troublesiare, on the other hand, usually quite easily dealt with, because I have reduced thewh, " to two simple facts, and because he can learn the how." Let me go further into this matter next week.