Subaru XT 1988 Service Manual page 1197

6-1 ENGINE ELECTRICAL SYSTEM
6) Remove the nuts securing the fan guide, and remove the Checking negative side diodes
fan guide.
Diode ASSY
Fan guide
L6-1466
Fig.
29
7) (This procedure is unnecessary when the diode is normal.)
Cut off rivet which holds diode ASSY to brush holder
terminals with a dri II. Unsolder termi nal L and brush holder,
and remove brush holder and IC regulator from diode ASSY as
a unit.
a) Brush holder and I C regulator are a one·piece type. Be
careful not to apply shocks or load to cooling fin.
b) Do not remove rivet unless diode is replaced.
L6-1467
Fig. 30
INSPECTION AND REPAIR
DIODE
Checking positive side diodes.
Terminal BAT (Positive side diode)
Tester lead Positive
CB Negative
~~,
U
Positive
(-£
-
No continuity
V
W
Negative
'8
Continuity -
16
Terminal E (Negative side diode)
U
V
W
::::: side
diode
2
side
diode
Tester lead Positive
'E
Positive
-r
-
Negative
e
No continuity
Terminals from stator coil
u
v
w
-:- E
Direction of current flow
Fig. 31
Negative 8
Continuity
-
I··--··~
; L
I
---: ___ . .J
E6-057
The diode allows current to flow in only one direction as
shown in the figure. If continuity is noted when connecting
tester leads in the normal direction (for example, BAT and
WI,
the diode is normal; if no continuity is noted, the diode is
faulty. On the contrary, if tester leads are connected in the
reverse direction, no continuity means a normal diode, while
continuity means a faulty diode.
If any diode is proven faulty in the above check, repoace the
diode assembly. The auxiliary diode have no terminals, and
must be checked for continuity by connecting tester leads to
both terminals of this diode.
Never use a megger or other high voltage insulation tester for
this test; otherwise, diodes may be damaged.
ROTOR
1) Slip ring wear limit
Measure the outer diameter of the slip ring. If worn more than
1 mm (0.04 in) from the standard dimension, replace the rotor
assembly.
Outer diameter of slip ring:
Standard
27.0 mm (1.063 in)
Wear limit:
26.0
mm
(1.024
in)