Fault Finding On 11 Ac; Checking The Field Isolating Relay; Checking The Alternator And Control Box; Checking Or Adjusting The Voltage Setting - Perkins 4.108 Workshop Manual

ELECTRICAL EQUIPMENT-Q.2
Any variance in the above data could indicate a fault
and the following procedure should be adopted before
disconecting any components.
The regulator is a sealed unit and is non-repairable
and if found to be faulty it must be replaced.
Warning Lamp does not light when switched "On".
Check the bulb.
If no fault
Check all wiring connections at regulator, alternator
and battery.
If no fault
Switch off, disconnect 'F' lead at regulator and connect
it to the negative terminal.
Switch on. If warning lamp lights up, the regulator is
faulty. If lamp fails to light up, the alternator is faulty.
Warning Lamp does not go out and Ammeter shows no
output when running.
Check all regulator, alternator and battery connections.
If no fault
Switch off, disconnect 'F' lead at regulator and connect
to regulator negative terminal.
Switch on, and run at fast idle.
If no output, alternator is faulty.
If output appears, regulator is faulty.
Warning Lamp does not go out when running and
Ammeter shows reduced output with full output only at
maximum speed or Warning Lamp goes out but
Alternator delivers reduced output. Full output only at
maximum speed.
Alternator faulty. Remove from installation and apply
open circuit diode check.
Warning Lamp flashes intermittently and Ammeter
needle oscillates when Battery is fully charged and no
loads are switched in.
Check for excessive resistance in regulator negative
sensing lead.
If no fault, regulator is faulty.
Batteries overcharging and Ammeter indicates high or
full output all the time.
Check regulator positive sensing lead and its connec-
tion at regulator.
If no fault, regulator is faulty.
4. Fault Finding on 11 AC
If the alternator does not produce its rated output of
43 amperes for 12 volt and 23 amperes for 24 volt
circuit, the failure may be due to any unit or the
associated wiring, and the following procedure should
be followed.
TEST 1
Checking the Field Isolating Relay
Disconnect the earthed battery terminal and the cable
from the alternator main output terminal. Connect a
0-60 DC ammeter between the terminal and dis-
connected cable. Link terminals 'C1' and 'C2' on the
field relay. Reconnect the battery cable. Close the
master switch and start engine and run at charging
speed. If ammeter shows a charge the relay is faulty,
or its wiring and connections.
If ammeter shows no charge, carryon with Test 2.
TEST 2
Checking the Alternator and Control Box
Leave the test ammeter connected, and disconnect
cables 'F' and ' - ' from control unit and join them
together. Remove link from field relay terminals and
ensure they are connected to 'C1' and 'C2'. Start
engine and run at charging speed.
Ammeter should indicate current values at 35 amps or
more for 12 volt circuit or 22 amps or more for 24
volt circuit. A zero or low reading indicates a faulty
alterator.
If satisfactory output is recorded, a faulty control unit
is indicated.
TEST 3
Checking or Adjusting the Voltage Setting
The regulator of the 4 TR control unit must be set on
CLOSED CIRCUIT, when the alternator is under load.
Also, the system must be stabilised before checking or
resetting is carried out, and the battery must be in a
well charged condition. Check the battery to control'
unit wiring, to ensure that the resistance of the com-
plete circuit does not exceed 0.1 ohm. Any high resist-
ance must be traced and remedied. Connect a test DC
voltmeter (suppressed zero type) scale 12 15 volts
for 12 volt installations or 24-30 volts for 24 volt in-
stallations, between the battery terminals, and note the
reading with no electrical load. Disconnect battery
earth cable and connect test ammeter between alter-
nator main terminal and disconnected cable. Re-
connect battery earth cable, and switch on an electrical
load of approximately two amps, such as, side and tail
lights. Start engine and run at about 2000 rev/min for
at least eight minutes. If the charging current is still
greater than 10 amps, continue to run engine until
this figure is reached. Then compare the voltmeter
reading with the appropriate setting limits, as specified
for the particular control unit as follows.
12 V (37423)/(37449)
24 V (37444)/(37502)
12 V (37429)
13.9 - 14.3 volts
27.9 - 28.3 volts
13.7 -14.1 volts
(Part no. marked on upper edge of the moulded cover
of Control Unit).