Vaz 21213, Руководство по ремонту, Страница: 146 / 222

An illuminated bulb advises about short-circuit in one or more
supplementary diodes.
The damaged diode can be identified only after removing the
diode plate and checking each diode.
Discontinuity in the supplementary diodes can be detected
with an oscilloscope through distortions in the voltage waveform
across terminal 61 and also by low voltage (below 14 volts) across
terminal 61 at a medium rate of the alternator rotor.
Voltage regulator - testing
The function of the voltage regulator is to continuously adjust
the field current flow to the alternator so that the alternator volt-
age is maintained within the preset range at various speed / load
conditions of the alternator operation.
In-vehicle test. For this test you need a DC voltmeter with
15-30 volt scale and accuracy of at least 1.0 class.
Run the engine for 15 minutes at medium speeds with the
headlights on, measure the voltage between the alternator termi-
nal 30 and alternator earth. The reading should be within 13.6-
14.6 volts.
When battery undercharge or overcharge becomes repeti-
tive, while the adjustable voltage falls outside the specification,
the voltage regulator must be renewed.
Off-vehicle test. For testing the voltage regulator, removed
from the alternator, make the connections as shown in Fig.7-10.
The pre-1996 voltage regulator should be tested complete with
the brush holder (Fig.7-10, b), since at the same time you can
detect a broken brush connection or a poor contact between the
voltage regulator terminals and brush holder.
Connect a test lamp of 1-3 watt, 12 volts across the brush ter-
minals. The terminals «Ç», «Å» (when available) and earth ter-
minal should be connected first to the power supply of 12 volts
and then to that of 15-16 volts.
With the sound voltage regulator, the lamp illuminates in the
first case and goes out in the second case. If the lamp illuminates
in both cases, there must be a break in the voltage regulator; when
the bulb fails to light in both cases, the regulator circuit is broken or
brush-to-regulator connection is loose (for pre-1996 alternators).
Capacitor - testing
The suppression capacitor is intended to protect the on-
board electronic equipment against voltage surges in the ignition
system along with suppression of radio interference.
A damaged capacitor or its loose fitting to the alternator (poor
ground) is recognizable through increased radio interference with
the engine running.
A simple way of testing the capacitor is to use a megohm-
meter or a tester (scaled as 1-10 åéhm). In case of a sound
capacitor, when its contacts are closed via the instrument, the
needle should first deflect towards a lower resistance values and
then gradually return to the initial position. The capacitance mea-
sured with a special device should be 2.2 microfarad ± 20%.
Alternator - overhaul
Alternatzor - dismantling
Clean the alternator and blow dry with compressed air.
Release the clip to disconnect air intake 3 (Fig.7-11) from hous-
ing 4. Undo two screws 1 and nut from contact bolt extension 5,
144
Fig.7-10. Checking the voltage regulator:
a
- 1996-on voltage regulator; b - pre-1996 voltage regulator; 1 - battery; 2 - voltage regulator earth ; 3 - voltage regulator; 4 - voltage regulator terminal «ò»; 5 - voltage
regulator terminal «B»; 6 - warning light; 7 - voltage regulator terminal «Å»
Fig.7-9. Checking the supplementary diodes:
1 - battery; 2 - warning light; 3 - alternator