Piper COMANCHE PA-24-180 Service Manual page 564

current rting.
The specified voltage nd the A
current rating values are found in paragraph
9-57.
. If the reading is the same as the cal-
culated value, proceed to part b.
2. If reading is much higher (infinite)
than the calculated value, proceed to part b.
3. If reading is zero, check for a short
between "NEG" and "FLD" leads, or for a
grounded "FLD"
lead. Circuit trace will be
burned open between points A-A, B-B, or C-C,
Figure 9-26.
4. If reading is low, alternator field
winding is shorted. Circuit trace may be burned
between points A-A, B-B, or C-C, Figure
9-26.
FIGURE 9-26. REGULATOR CHECKS
NOTE
To expose the printed circuit for viewing, remove the bottom place
from the regulator, the three panel board attaching screws, the
transistor attaching screws, and then separate the heat sink from
the panel board.
b. With switch turned ON, connect voltmeter as shown in Step. 2 Figure 9-24. Make sure posi-
tive (+) and negative (-) voltmeter leads are connected as shown.
c. If meter reads battery voltage, disconnect lead at alternator "F1" (field) terminal.
1. If reading is still battery voltage, wiring is not defective, and no more wiring tests need
be made.
2. If voltage reading is zero, the "NEG" and "FLD" leads are reversed. Circuit trace
will be burned open between points A-A, B-B, or C-C, Figure 9-26.
d. If meter reads zero voltage,disconnect lead at alternator "Fl''(field) terminal, and connect
a jumper lead from this lead to the battery positive (4) post. See Figure 9-25.
1. If meter now reads battery voltage, the "POS" and "FLD" leads are reversed. This
misconnection alone will not cause the circuit trace to be burned open.
2. If meter now reads backwards, alternator field terminalis connected to regulatornegative
terminal, the positive line is connected to regulator field terminal, and regulator positive terminal
is connected to negative side of circuit. Either the circuit trace will be burned between points
C-C, D-D, or E-E, Figure 9-26; or the driver transistor will be open. In either case, the driver
bias resistor will have been overheated.
e. If voltmeter reads backwards, disconnect lead at alternator "Fl" (field) terminal.
1. If meter still reads backwards, the "POS" and "NEG" leads are reversed. The circuit
trace may be burned between points C-C, D-D, E-E, or F-F, Figure 9-26. The transient suppres-
sion diode always will be open or shorted.
2. If meter now reads zero, the positiveline is connected to regulator 'NEG" terminal, the
negative line is connected to the regulator "FLD" terminal, and the alternator 'Fl" (field)
ELECTRICAL SYSTEM
ISSUED: 8/18/72
3 B18
PIPER COMANCHE SERVICE MANUAL