Electrical Equipment; Alternator; Fault Finding On Ac5 - Perkins 4.108 Workshop Manual

ALTERNATOR
Models AC5, HAC, 15ACR and 17 ACR
1. Precautions
The diodes in the alternator function as one-way· valves
and the transistors in the regulator/control box operate
as fast switches. Both are accurate and sensitive.
They do not wear out and seldom require adjustment,
but because they are sensitive to voltage changes and
high temperature, the following precautions are vital to
prevent them from being destroyed.
(a) DO NOT disconnect the battery whilst the engine
is running. This will cause a voltage surge in the
alternator charging system that will immediately
ruin the diodes or transistors.
(b) DO NOT disconnect a lead without first stopping
the engine and turning all electrical switches to
the off position.
(c) DO NOT cause a short circuit by connecting leads
to incorrect terminals. Always identify a lead to its
correct terminal. A short circuit or wrong con-
nection giving reverse polarity will immediately
and permanently ruin transistors or diodes.
(d) DO NOT connect a battery into the system without
checking for correct polarity and voltage.
(e) DO NOT "flash" connections to check for current
flow. No matter how brief the contact the tran-
sistors may be ruined.
2. Maintenance
The alternator charging system will normally require
very little attention, but it should be kept free from
build-up of dirt, and a check made if it fails to keep the
battery charged.
(a) Regularly inspect the driving belts for wear and
correct tension. It is important to ensure that all
belts on a multiple belt drive have equal tension
and are each carrying their share of the load. Slack
belts will wear rapidly and cause slip which will
not drive the alternator at the required speed.
Drive belts which are too tight impose severe side
thrust on the alternator bearings and shorten their
life. Periodically ensure that the alternator is
correctly aligned to the drive.
(b) Do not replace faulty belts individually in a mUlti-
belt system. A complete matched set of drive belts
must always be used.
(c) Keep the alternator clean with a cloth moistened in
kerosene or cleaning fluids. Ensure that ventilation
slots and air spaces are clear and unobstructed.
SECTION
Q
Electrical Equipment
(d) Remove any dirt accumulated on the regulator/
control box housing, and ensure that cooling air
can pass freely over the casing.
3. Fault Finding on AC5
The AC 5 alternator is so designed that a flow of
current indicated either by the extinguishing of the
warning light, or as shown on the ammeter, is suffiicient
evidence that the system is in proper working order.
Therefore, no open circuit, voltage or current output
checks should be performed in the installation UN-
LESS:-
(a) The warning light fails to illuminate when the
generator is stationary, and the switch is closed
OR fails to become extinguished when the alter-
nator is running.
(b) No charging current is shown on ammeter.
(c) The battery is flat.
(d) The battery is "boiling", indicating loss of voltage
control.
If any of the above symptoms occur, the procedure in-
dicated below should be followed.
(a) Connect a good quality moving coil voltmeter
0-50 volts range across the battery or regulator
negative terminal, and one of the three positive
terminals marked LO, MED, HI. Disconnect alter-
nator output terminal. Fit a good quality moving
coil 0 - 100 amp ammeter in series with the
alternator terminal and output lead. The battery
should be in a charged condition.
(b) Close the warning light switch (master electric
switch on dashboard) when the warning lamp
should light up.
(c) Switch on a 10-15 amperes load such as lights,
etc. for fifteen minutes.
(d) Start engine and run at fast idle speed with fans,
etc, for fifteen minutes.
1. The warning light should go out.
2. The ammeter records a small charge depen-
dant on engine speed.
(e) Increase engine speed momentarily to maximum
speed, when the charging current should be about
30 Amperes for 24 Volt, and 53 Amperes for 12
volt systems.
(f)
With the alternator running at approximately half
speed, (engine speed about 1,500 rev/min) switch
off electrical load. Depending on the connection
selected for the positive sensing wire LO; MED
or HI, the voltage should rise to between 26 and
28 volts on 24 volt systems and 13-14 volts on 12
volt systems and then (emain constant. At the
same time the current reading should drop
appreciably.