Piper COMANCHE PA-24-180 Service Manual page 563

9-58. Reulater. (Delce-Reny)
9-59. Checking Regultor Circuit. Altenator failures may be caused by circuit misconnections,
such ereversed
leads or shorted or gounding of terminals with a screwdriver, etc. The following
provides a means of locating circuit misconnection. It also covers the different types of regulator
panel board circuit rce defects which indicate a certain type of wiring harness misconnections.
A burned circuit trace on the regulator panel board is proof that a circuit misconnection exists, or
occurred at some time. However, a misconnection will not always cause a burned circuit trace
even though circuit component failures have been caused.
Before installing a new regulator, it is very important to make sure that no wiring circuit
defects or wiring harness misconnections exist. If the wiring harness is defective, or if miscon-
nections exist, the new regulator will fail too. Futhermore, repeated replacement of regulators
will only result in repeated regulator failures, and this will continue until the circuit defect is
corrected.
To check the wiring harness for defects or misconnections before installing the new regu-
lator, observe the following procedure.
NOTE
Meter connections are made to the harness connector that has been
unplugged from the regulator.
a. Check the alternatorfield resistance with an ohmmeter as shown in Step L. Figure 9-24 and
note the reading. Make sure the master switch is OFF. Readings of less than 2 ohms, or more
than 8 ohms indicate a defective field winding in the alternator or a defective wiring harness. If
the reading is within the 2 to 8 ohm range, check the reading against the allowable resistance in
the circuit which can be calculated by dividing the specfied voltage for the alternator by the
OHMMETER
TYPICAL
FIGURE 9.24. VOLT - OHMMETER TEST FIGURE 9.25. JUMPER CONNECTION
ELECTRICAL SYSTEM
ISSUED: 81872
3 B17
PIPER COMANCHE SERVICE MANUAL