Cessna 150M - Page 216

16-38. TROUBLE SHOOTING THE ALTERNATOR SYSTEM (Cont).
TROUBLE
ALTERNATOR
SYSTEM
WILL NOT KEEP BAT-
TERY CHARGED.
16-10
PROBABLE CAUSE
Regulator faulty or improp-
erly adjusted.
Faulty wiring between alter-
nator and regulator, or
faulty alternator.
REMEDY
1.
Start engine and adjust for
1500 RPM. Ammeter should
indicate a heavy charge rate
with all electrical equipment
turned off. Rate should taper
off in 1-3 minutes. A voltage
check at the bus should indicate
a reading consistant with the
voltage vs temperature chart
on page 16-10. If charge rate
tapers off very quickly and
voltage is normal, check bat-
tery for malfunction. If am-
meter shows a low charge rate
or any discharge rate, and
voltage is low, proceed to step
2.
2. Stop engine, remove cowl,
and
remove cover from voltage
regulator. Turn master switch
ON/OFF several times and ob-
serve field relay in regulator.
Relay should open and close with
master switch and small arc
should be seen as contacts open.
If relay is inoperative, proceed
to step 3. If relay operates,
proceed to step 4.
3. Check
voltage at "s" terminal
'of regulator with master switch
closed. Meter should indicate bus
voltage. If voltage is present, re-
place regulator. If voltage is not
present, check wiring between
regulator and bus.
4. Remove plug from regulator
and start engine. Momentarily
jumper the "A+" and "F" termi-
nals together on the plug. Ship's
ammeter should show heavy rate
of charge. If heavy charge rate
is observed, replace regulator.
If heavy charge rate is not ob-
served, proceed to step 5.
5. Check resistance from "F"
terminal of regulator to "F" ter-
minal of alternator. Normal
indication is a very low resis-
tance. If reading indicates no,
or poor continuity, repair or
replace wiring from regulator
to alternator.