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ELECTRICAL SYSTEMS
TROUBLE DIAGNOSIS
10-11
bulb.
If
left signal lamp flashes on left turn,
how-
ever, trouble is in indicator bulb. The opposite
applies for inoperative left indicator light.
If
both indicator lights flash rapidly but dimly
at the same time, look for burned out bulb in
either the front or rear signal lamp on side for
which signal switch is set.
If
bulbs are okay
check for improperly connected wires at tail
lamp or terminal block beside radiator.
If
both
indicator lights burn dimly at the same time,
without flashing, look for burned out bulb at
both front and rear signal lamps.
If
neither the signal, stop, or back-Up lights
burn,
replace
direction signal fuse
.
If
stop and
back-up
light s burn but none of signal light s
burn, replace flasher.
If
both indicator lights
remain
on with signal switch in neutral position,
replace flasher.
If
flasher, or fuse, continually burns out,
check for short circuit (ground) in indicator
light sockets or at terminal blocks beside
radiator.
d. Horns
Fail t
o
Blow
1.
Bridge between horn (H) and battery
(B) terminals of horn relay with heavy jump-
er wire or screwdriver.
If
horns do not blow,
adjust horns (par. 10-60).
2.
If
horns blow when (H) and (B)
ter-
minals are bridged, ground relay terminal (S)
to which small black wire is connected.
If
horns
do not blow, adjust horn relay (par. 10-61).
3.
If
horns blow with (S) terminal grounded,
check for open circuit in wiring between relay
and horn button and check horn
button con-
tacts, using 6-volt test lamp. This circuit can
be broken at horn cable connector on left side
of steering column jacket.
10-13 INSTRUMENTS AND CLOCK-
TROUBLE DIAGNOSIS
a
.
Temperature Gauge
If
the temperature gauge appears to be de-
fective it can be tested before removal. Drain
water from radiator, then carefully remove the
vapor pressure bulb from cylinder head. Place
bulb in a pail of hot water, also, put a reliable
thermometer in water, and allow to set for
three minutes.
If
gauge pointer
registers
the
same as
t
he thermometer, the gauge is okay,
otherwise
'
it will be necessary to replace the
complete gauge
assembly.
When pr essur e bulb
is inst all ed in cylinder hea d be sure to attach
bond strap
on tube to t
he dash
wi
th clean
tight connection to avoid radio interference.
b. Gasoline Gauge
If
gasoline gauge shows full under all con-
ditions look for an open circuit in line between
dash and tank units.
If
gauge shows empty
under all conditions look for ground in wiring
between dash and tank units or for reversed
connections on dash unit. See chassis wiring
circuit diagrams in Section 10-J.
If
check of wiring does not disclose cause of
trouble, test dash unit, wiring circuit, and tank
unit (par. 10-67).
c. Electric Clock
If
clock gains or loses time it may be regu-
lated by moving the regulator located on back
of clock (par. 10-66).
If
clock does not run, check the fuse.
If
fuse
is blown, check clock wiring circuit for short;
see chassis wiring circuit diagrams in Section
10-J.
With a Borg electric clock, the most frequent
cause of clock fuse blowing is low voltage at
the clock which will prevent a complete wind
and allow clock contacts to remain closed. This
may be caused by any of the following: dis-
charged battery; corrosion on contact surface
of battery terminals; loose connections at bat-
tery terminal on cranking motor solenoid
switch, charge indicator, light switch feed wire
or terminal connection on back of clock. There-
fore, if in reconnecting battery or clock it is
noted that the clock is not ticking always check
for blown fuse, and examine the circuits at the
points indicated to determine and correct the
cause.
d
.
Speedometer
If
speedometer pointer wavers, look for a
kinked cable and test speedometer head for
tightness or binding (par. 10-68).
If
speedometer registers neither speed nor
mileage look for broken cable.
If
cable is okay,
remove head for repairs by an
authorized
AC
Speedometer service station.
If
speedometer
shows speed but not mileage, or vice versa, the
head must be removed for repairs.
If
speedometer speed and mileage readings
are not accurate first check tires for proper
size.
If
tires are of correct size check speedom-
eter driven gear for correct number of teeth
(par. 4-3, c).
If
tires and driven gear are
cor-
rect, remove speedometer head and have it
checked by an authorized AC Speedometer
service station.
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