Testing Of Rectifier Assemblies Using Test Lamp - Piper Dakota Maintenance Manual

4. Touch metal strap of each of positive rectifiers with test probe.
a. A reading on tester of 1.75 amps or more indicates a satisfactory rectifier. Readings and direction
of needle movement must be same for all three rectifiers.
b. When two rectifiers are good and one is shorted, reading taken at good rectifiers will be low and
reading at shorted rectifier will be zero. Disconnect lead to rectifier reading zero and retest. With
defective rectifier disconnectcd, reading of good rectifiers will be within satisfactory range.
c. When one rectifier is open, tester will read approximately one amp while two good rectifiers will
read within satisfactory range.
TESTING OF NEGATIVE RECTIFIERS USING C-3829 TESTER (figure 24-6)
The plastic cases surrounding rectifiers are for protection against
corrosion and must not be broken. When performing tests,
always touch test probe to metal strap nearest rectifier.
l. Connect test lead alligator clip to rectifier end housing.
2. Touch metal strap of each negative rectifier with test probe and note reading of each.
3. The test indications for negative rectifiers are same as for positive rectifiers except test meter will read
on opposite side of scale.
If a negative rectifier shows shorted, isolate stator from rectifier
end shield and retest. It is possible that a stator winding could be
grounded to stator laminations or rectifier end shield which
would indicate a shorted negative rectifier.

TESTING OF RECTIFIER ASSEMBLIES USING TEST LAMP

l. Remove nuts from terminal block studs which secure stator windings and positive and negative
rectifier straps.
2. Lift off stator winding terminals and carefully pry stator assembly from end shield.
3. Test rectifiers with a l2-volt battery and a test lamp equipped with a number 67 bulb.
a. Connect one side of test lamp to positive battery post and other side of lamp to a test probe.
b. Connect another test probe to negative post of battery.
4. Place one test probe on rectifier heat sink and other test probe on strap on top of rectifier.
Note whether test lamp lights or does not light. Repeat test for each rectifier.
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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