Piper Comanche PA-24 Service Manual page 688

With the .talor discODDected, check a
diode in the heat link
by
cODDecliaa one of the
ohmmeter leads to the heat sink, ODd the other
ohmmeter leed to the diode lead, ODd note the
reldina (Filllre
~20).
Thea rev .... the ohm·
m.ter lead
CorlDectiOas,
ODd not. the .. adin&-
If both readia" ore very low, or if both .. adin"
a .. very
hip,
the diod. ia d.fective. It. aood
diode will live on. low .. adina and one biah
reedin&- Check the oth.r two diode. in the heat
sink in the sam. manner.
To cbeck a diode ",OWIted in tbe end
frame, connect one of the ohmmeter
l •• ds
to the
end frame. and the other ohmm.ter lead
to
tbe
diode lead (Figure
~20).
and note the readina.
Then reverse the ohmmeter lead connections.
and note the readina. If both reldin,s are very
low. or if both readin.s are very hiah. the diode
i. defective. It. ,ood diode will live one low
reldinS and one biah reading. Check the other
two diodes in the end frame in the
lame
manner.
PIPER COMANCHE SERVICE MANUAL
, I
~
OMMM"II
FIGURE 9·20. CHECKIHG D100ES
Test I.amp Method:
An
alte",ate method of cbeckina the diodes i. to use a test lamp of not
more !hOD 12-volts in place of the ohm .. eter.
CAUTIOH
Do not use 110-volt test lampi to check diode •.
With the stator discODnected., connect the test lamp leads across each diode as previously
described first in one direction and then in the other. If the lamp lipts in both checks. or fails to
light
in
both checkl. the diode il defective. When checking. good diode. the lamp will light in
only one of the two checks.
Special Tester )lethad: Special testers are available which operate without disconnecting
the statof. To
u.le
these testers,
follow
the tester
manufacturer's
recommendations.
9-50. Diode Replau .. enl. To replace
0
diode. ule a suitable tool to .upport the end frame or
heat sink, aDd use an. arbor preiS or vise to push the diode out. Also use a special tool which fits
over the outer diode edge to push the diode
in.
and support the beat sink and end frame
with
a
suitable tool.
HOTE
Diode replacement t0011 are available from various manuf ICturers
~ormally supplying tools and test equil'ment to the aviation in-
dustry .
EI.ECTRICAI. SYSTEM
ISSUED: 8118m
3
812
•