Cessna 177 SERIES Service Manual page 269

16-39A. TROUBLE SHOOTING THE ALTERNATOR SYSTEM (BEGINNING WITH 1978 MODELS) (CONT.)
b. ENGINE RUNNING (Cont.)
TROUBLE
PROBABLE CAUSE
REMEDY
ALTERNATOR SYSTEM WILL
Alternator output voltage
1. Connect coltmeter between
NOT KEEP BATTERY
insufficient.
D.C. Bus and ground. Turn off
CHARGED.
all electrical loads. Turn on
Battery Switch. Start engine and
adjust for 1500 RPM, voltage
should read approximately 24
volts. Turn on alternator switch,
voltage should read between 27.4
and 28.0 volts. Ammeter should
indicate a heavy charge rate which
should taper off in 1-3 minutes. If
charge rate tapers off very quick-
ly and voltage is normal, check
battery for malfunction. If am-
meter shows a low charge rate or
any discharge rate, and voltage
does not rise when alternator
switch is turned on proceed to
step 2.
2. Stop engine, turn off all
switches. Connect voltmeter
between "F" terminal of
alternator and ground. Do
NOT start engine. Turn on
battery switch and alternator
switch. Battery voltage
should be present at "F"
terminal, less 1 volt drop
thru regulator, if not refer
to step 3.
3. Starting at "F" terminal
of alternator trace circuit
to voltage regulator, at "B"
terminal of regulator trace
circuit to over-voltage sensor,
to master switch, to bus bar.
Replace component which does
not have voltage present at
output. Refer to alternator
system wiring diagram in
Section 20.
Alternator field winding
1. If voltage is present turn off
open.
alternator and battery switches.
Check resistance from "F"
terminal of alternator to alter-
nator case, turning alternator
shaft during measurement.
Normal indication is 12-20 ohms.
If resistance is high or low,
repair or replace alternator, If
OK refer to Step 2.
16-12B
Change 7