Cessna 150J - Voltage Regulator

16-38. TROUBLE SHOOTING THE ALTERNATOR SYSTEM (Cont. )
TROUBLE PROBABLE CAUSE
REMEDY
ALTERNATOR SYSTEM
WILL NOT KEEP BAT-
TERY CHARGED (Cont).
Faulty wiring between alter-
nator and regulator, or
faulty alternator (Cont).
6.
Check resistance from "F"
terminal of alternator to alter-
nator case. Normal indication
is 6-7 ohms. If resistance is
high or low, repair or replace
alternator.
7. Check resistance from case
of alternator to airframe ground.
Normal indication is very low
resistance. If reading indicates
no, or poor continuity, repair or
replace alternator ground wiring.
ALTERNATOR OVERCHARGES
BATTERY - BATTERY USES
EXCESSIVE
WATER.
Regulator faulty or improperly
adjusted.
Check bus voltage with engine
running. Normal indication
agrees with voltage vs temper-
ature chart on page 16-13. Ob-
serve ship's ammeter, ammeter
should indicate near zero after a
few
minutes of engine operation.
Replace regulator.
OVER-VOLTAGE WARNING
LIGHT
ON.
Regulator faulty or improperly
adjusted. Faulty sensor switch.
1. With engine running turn off
and on battery portion of the
master switch. If the light stays
on shut down engine then turn on
the "BAT and "ALT" portions of
the master switch. Check for
voltage at the "S" terminal of the
voltage regulator. If voltage is
present adjust or replace regula-
tor. If voltage is not present
check master switch and wiring
for short or open condition. If
wiring and switch are normal
replace sensor.
16-39. VOLTAGE REGULATOR.
16-40. DESCRIPTION. The alternator voltage regu-
lator contains two relays. One relay is actuated by
the aircraft master switch and connects the regulator
to the battery. The second relay is a two- stage,
voltage sensitive device which is used to control the
current applied to the field winding of the alternator.
When the upper set of contacts on the voltage regula-
tor relay are closed, full bus voltage is applied to
the field. This condition will exist when the battery
is being charged or when a very heavy load is applied
to the system. When the upper contacts open, as the
voltage begins to rise toward normal bus voltage, the
voltage to the alternator field is reduced through a
resistor network in the base of the regulator thus re-
ducing the output from the alternator. As the voltage
continues to rise, assuming a very light load on the
system, the lower contacts will close and ground the
alternator field and shut the alternator completely off.
Under lightly loaded conditions the voltage relay will
vibrate between the intermediate charge rate and the
lower (completely off) contacts. Under a moderate
load, the relay will vibrate between the intermediate
charge rate and the upper (full output) contacts. The
voltage relay is temperature compensated so that the
battery is supplied with the proper charging voltage
for all operating temperatures. With the battery
fully charged (ship's ammeter indicating at or near
zero) and a moderate load applied to the system (a
taxi light turned on) the voltage at the bus bar should
be within the range shown according to the air tem-
perature on the following chart:
16-11