Piper Comanche PA-24 Service Manual page 694

~t
ratiD&- The specified volta. ...d the
CDmtllt ratiDa .alues are fouad ia para"aph
'·57.
1. If the readina ia the ..... u the cal·
culated value, proceed
to
part b.
2. If ..
adiDa is IllUch hiper (iafiaite)
thaa the calculated .alue, proceed to part b.
3. If readiDl i. zero, . check for a short
betw ..
n "NEG" ud "FLO" leads, or for a
arouaded "FLO" lead. Circuit trace
_ill
be
bumed open betwHD points A·A. 80S, or C·C.
FillUre 9-26.
4. If .. adiDa is 10_. altemator field
.,indina is shorted. Circuit trace may be burned
betweea paiato A·A. 80S. or C.C. Fiaure
9-26.
HOTl!
PIPER COMANCHE SERVICE MANUAL
FIGURE 9.26. REGULATOR CHECKS
To expose the priated circuit for vie.,iDa, remove the botto .. plate
from the rellliator. the three
p .... 1
board attachina screws, the
transistor attachiDl screws, aDd thea separate the beat siak from
the p ... el board.
b. With switch tumed ON. CQDDect voltmeter as sbown ia Step. 2, FillUre 9-24. Make sure posi-
tive
(+)
and necative (-) voltmeter leads are conaected .. sbown.
c. U meter reads battery voltage.
diSCOIIDKt
ieed at alternator uFl" (field) terminal.
1. If reading is still battery Yolta,e, wiri1lg is not defective. and no
iliON
wiri~1
tests need
be made.
2. If yoltage reading is zero, the "NEG" and "FLO" leads are reversed. Circ:\ut trace
"'iU be burned open bet.,een paints A·A, 80S. or C.C, Ficure 9-26.
d. If meter reads zero yoltap.dilcoanect lead at Iltemator UFl"(field) terminal. and connect
a jumper lead from this lead to the battery pasitive
(+)
post. See Fi ..... 9-25.
1. U
meter now read. battery yolta., the
"POS" and "FLO" leads
Ire
reversed.
This
IIlilcOIIfteCtiOil
alone will not caue the circuit trace to be bumed open.
2.
If
meter now reads backwards, altemator field terminal is connected to regulator negative
terminal, the positive line is connected to replator field terminal, and reaulator positive terminal
is connected to nelative side of Circuit. Either the circuit treee will be bumed between pointS
C·C. D-O. or E·E, FillUre 9-26; or the driver transistor will be open. In either case. the driver
bias resistor will have been overheated.
e. If volaaeter reads baclcwsrds. disconnect lead at altemator "FI" (field) terminal.
1. If meter still reads backwards, the "POS" and "NEG" leads are reversed. The cirCUit
trace .. ay be burned between paints C·C. D-O. E.E, or F.F. Fieure 9-26. The transient suppres·
sion diode always .,ill be open or shorted.
2.
If
meter now reads zero, the positive Une is connected. to regulator
'~EG"
terminal. the
neptive liDe is connected to the regulator
"FLO" terminal. aDd the alternator 'F!" (field)
ELECTRICAL SYSTEM
ISSUED:
8/1ln2
3 818