Piper COMANCHE PA-24-180 Service Manual page 536

PIPER COMANCHE SERVICE MANUAL
9-5. Checking Generator System. In analyzing complaints of generator-regulator operation, any of several
basic conditions may be found (Refer to Figure 9-1 )
a. Fully Charged Battery and Low Charging Rate This indicates normal generator-regulator
operation. Regulator setting may be checked as outlined in the following section.
b.
Fully Charged Battery and a High Charging Rate - This indicates that the voltage regulator is
not reducing the generator output as it should A high charging rate to a fully charged battery will damage the
battery and the accompanying high voltage is very injurious to all electrical units
This operating condition may result from
1.
Improper voltage regulator setting.
2.
Defective voltage regulator unit.
3 Grounded generator field circuit (in either generator. regulator or wiring)
4 Poor ground connection at regulator.
5.
High temperature which reduces the resistance of the battery to charge so that it will accept a
high charging rate even though the voltage regulator setting is normal.
If the trouble is not due to high temperature. determine the cause of trouble by disconnecting the
lead from the regulator"F"terminal with the generator operating at medium speed f the output remains high.
the generator field is grounded either in the generator or in the wiring harness. If the output drops off. the
regulator is at fault, and it should be checked for a high voltage setting or grounds
c. Low Battery and High Charging Rate This is normal generator-regulator action Regulator
settings may be checked as outlined in the following section.
d. Low Battery and Low or No Charging Rate - This condition could be due to
I
Loose connections,
frayed or damaged wires
2 Defective battery
3
High circuit resistance
4 Low regulator setting
5 Oxidized regulator contact points
6 Defects within the generator
If the condition is not caused by loose connections. frayed or damaged wires, proceed as follows to
locate cause of trouble.
To determine whether the generator or regulator is at fault. momentarily ground the "F" terminal
of the regulator and increase generator speed. If the output does not increase, the generator is probably at
fault and it should be checked as outlined in the Generator Section. If the generator output increases, the
trouble is due to
I A low voltage (or current) regulator setting
2.
Oxidized regulator contact points which insert excessive resistance into the generator field
circuit so that output remains low
3 Generator
field circuit open within the regulator at the connections or in the regulator
winding
e Burned Resistances, Windings or Contacts - These result from open circuit operation or high
resistance in the charging circuit Where burned resistances. windings or contacts are found. always check
wiring before installing a new regulator Otherwise, the new regulator may also fail in the same way
ISSUED: 8/18/72
3A14
ELECTRICAL SYSTEM
3A14