Perkins 4.99 - Electrical System Testing; Alternator Output Test and Regulator Test; Dynamo Description and Operation

ELECTRICAL EQUIPMENT -Q.4
Alternator Output Test with Regulator
Inoperative
Withdraw the two-part connector from the alternator,
remove the
moulded cover (secured by two screws)
and link together regulator terminals 'F' and '-'.
Connect an external test circuit to the alternator output
terminals as shown in Fig. Q.1.
B +
+
INO
'--------iAI------.
0)
CD
~--------iVI_------_1I
01
1. 12 volt 2.2 watt Bu Ib
2. 0-40 or 0-60 Ammeter
3. 12 volt Battery
4. 0-20 Voltmeter
5. 0-15 ohm 35 amp Variable Resistor
Observe carefully the polarity ot battery and alternator
terminals - reversed connections will damage the
alternator diodes.
The
variable resistor across the battery terminals must
not be left connected for longer than is necessary to
carry out the following test.
Start
the engine. At 1,500 rev/min (alternator speed),
the test circuit bulb should be extinguished. Increase
engine speed until the alternator is running at 6,000
rev/min approximately, and adjust the variable resist-
ance until the voltmeter reads 14.0 volts. The ammeter
reading should then be approximately equal to the
rated
output (See previous paragraph). Any appreci-
able deviation from this figure will necessitate the
alternator being removed from the engine for further
examination.
Failure of one or more of the diodes will be indicated
in the above test by effect on alternator output, and
also in some instances by abnormally high alternator
temperature and noise level.
Regulator Test
The following test assumes the alternator to have been
tested and found satisfactory.
Disconnect the variable resistor and remove the link
bridging regulator terminals 'F' and '-'.
With the remainder of the test circuit connected as for
the alternator output test, start the engine and again
run the alternator up to 6,000 rev/min until the ammeter
shows an output current of less than 10 amperes. The
voltmeter should then give a reading of 14.0 - 14.4
volts. Any
appreciable deviation from this (regulating)
voltage means that the regulator is not functioning
properly and must be replaced.
If the
foregoing tests show the alternator and regulator
to be satisfactorily performing, disconnect the test cir-
cuit and reconnect the alternator terminal connector.
Now connect a low-range voltmeter between the posi-
tive
terminal of the alternator (the moulded terminal
connector is open-ended to faciltate this) and the posi-
tive
terminal of the battery. Switch on battery load
(headlights etc.), start the engine and increase speed
until the alternator runs at approximately 6,000 rev/min.
Note the voltmeter reading.
Transfer the voltmeter connections to the negative
terminals of alternator and battery and again note the
meter reading.
If
the reading exceeds 0.5 volt on the positive side or
0.25 volt on the negative side, there is a high resistance
in the
charging circuit which must be traced and
remedied.
DYNAMO
The following information in concerned with the Lucas
C40-1 model. Should information be required in con-
nection with any other type of dynamo then the rele-
vant
manufacturer should be contacted.
The C40-1 is of extruded yoke construction and is a
ventilated type. Holes in each end bracket allow a
pulley mounted fan to draw cooling air through the
dynamo.
Description
It is a shunt wound, two pole, two brush machine
designed to work in conjunction with a compensated
voltage control regulator unit. A ball bearing supports
the armature at the driving end and a porous bronze
bush
at the rear supports the commutator end.
The
output of the dynamo is controlled by the regulator
unit and is dependent on the state of charge of the
battery and the loading of the electrical equipment in
use. When the
battery is in a low state of charge, the
dynamo gives a high output, whereas if the battery is
fully charged, the dynamo gives only sufficient output
to keep the battery in good condition without any
possibility of overcharging. An increase in output is
given to balance the current taken by lamps and other
accessories when in use.
When fitting a
new control box, it is important to use
only an authorised replacement. An incorrect replace-
ment can result in damage to the dynamo.