| SWITCH BOX REPAIR SECTION FROM MORRIS COMMERCIAL SEP. 1940 SERVICE MANUAL. |
ELECTRICAL SECTION (SWITCH GEAR AND INSTRUMENTS)
Ammeter Readings
The
ammeter indicates the amount of current passing into or out of the
battery. Supposing that the dynamo is generating 7 amperes and that some
of the side and tail lamps are in use, taking, together with the
ignition coil, 3 amperes, then 4 amperes are left for charging the
battery. This is the reading given on the ammeter.
With compensated
voltage control equipment it must be remembered when noting ammeter
readings that normally during daytime running, when the battery is in
good condition, the dynamo gives only a trickle charge so that the
charge, reading will seldom be more than 3 or 4 amperes.A discharge
reading may lie given immediately after switching on the headlamps. This
usually happens after a long run when the voltage of the battery is
high. After a short time the battery voltage will fall and the regulator
will respond, causing the dynamo output to balance the load.When
starting from cold the charging current will.rise until it reaches a
steady maximum at a speed of, say, 20 miles per hour, after which it
will remain fairly high for about 10 minutes, then fall to a steady
charge which is most suitable for the particular condition of the
battery.
Checking Ammeter Readings
To
check the accuracy of the ammeter readings, connect an ammeter in
series with it and compare the readings of the two instruments.It must
lie remembered that the ammeters used on motor vehicles are not
precision instruments, as they are designed to withstand the excessive
vibration that is possible under had road conditions. These instruments
are, however, sufficiently accurate for checking the normal operation of
the equipment.
Ammeter Fails to Indicate
Usually
caused by the ammeter being overloaded due to a short circuit in the
wiring between the ammeter and the cut-out and fuse unit. Examine the
wiring for evidence of damage and fit replacement ammeter.
In the
event of an open circuit in the ammeter indicated by the lamps and
accessories not operating when switched on, the ammeter can be "shorted"
by joining its two terminals by means of a length of wire until a
replacement can he fitted.
Switch Units
Occasionally,
say when the vehicle is taken down for a general overhaul, the
terminals of the switch should be examined and, if necessary, tightened.
Remove any stray strands of wire which may cause a short circuit.
Switchboard. (C.A.V. Type No. 47)
This
switchboard being only 3.5” (89 mm.) face-plate diameter, is a compact
unit for flush fitting into a dashboard or panel. If sufficient slack is
allowed in the cables the complete board can he withdrawn from the
front of the dashboard by removing the clamp and the two nuts securing
it in position at the back.
The board is fitted with a main rotarv
switch for the control of the tail, side and tail, head side and tail
lamps, together will an additional turn switch fur ignition control.
Either magneto or coil may be used, but it is not suitable for dual
ignition. Dynamo charging is indicatcd by a red pilot light fitted to
the right of the ignition switch. |
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