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PART 15-1- GENERAL LIGHTING SYSTEM, HORNS INSTRUMENTS SERVICE
15-5
so be installed, regardless of its ap-
parent condition.
nSTING
Refer to Group
22
for schemat-
ics and locations of wiring harnes-
ses.
HORN TEST
The only test necessary on the
horn is for current draw.
Current Draw Test
Connect a voltmeter and ammeter
to the horn and to a voltage supply
as shown in Fig. 2. The normal
current draw for the horns at
12
volts is 4-5 amperes.
N;~~~~
LEAD
~
v
~
POS.I~
LEAD
~
-4~-...,.--
+
FIG. 2 -Horn Current
Draw
Test
HEADLIGHT SWITCH AND
BEAM SELECTOR SWITCH TESTS
The following tests may be made
to determine whether a headlight
switch or a beam selector sw1tch is
defective:
Turn on the headlights, and oper-
ate the beam selector switch. If none
of the headlights turn on when the
beam selector switch is operated, yet
the instrument panel lights operate,
the headlight switch or the red-yel-
low stripe wire from the headlight
switch to the beam control switch is
probably
defective.
Suhstitute
a
known good switch for the suspected
switch to determine whether the
switch or the wiring is at fault.
If the headlights operate only with
the beam selector switch in one posi-
tion, the selector switch or the wir-
ing from the switch to the headlight
is defective. Substitute a known good
selector switch for the suspected
switch to determine whether the
switch or the wiring is at fault.
CONSTANT VOLTAGE
REGULATOR TEST
The instrument cluster must be re-
moved to gain access to the voltage
regulator and gauge terminals.
Turn the ignition switch on, check
for voltage at the fuel gauge upper
terminal (Falcon) temp gauge term-
inal adjacent to the regulator screw.
The
voltage should oscillate be-
tween
zero
and
about
10
volts. If it does not, the constant
voltage regulator is defective, or
there is a short to ground between
the voltage regulator and the gauges.
If a gauge unit is inaccurate or
does not indicate, replace it with a
new unit. If the gauge unit still is
erratic in its operation, the sending
unit or wiring to the sending unit is
faulty.
If both the fuel gauge and the
temperature gauge indicate improp-
erly and in the same direcdon, the
constant voltage regulator could
be
defectin, as it supplies both gauges.
TESTING FUEL AND
TEMPERATURE GAUGES
FUEL GAUGE.
A simple check to show whether it
is the sender unit or gauge unit at
fault is to fit a known good sender
unit in the circuit.
If the gauge unit reads propor-
tionate to the float setting, the gauge
unit is correct
.
Do not test gauge units by shorting
terminals direct to earth. Minimum
circuit resistance is to be held to
10
ohms for high indication. Lower
resistances will destroy calibration.
TEMPERATURE GAUGE TEST
Start the engine and allow it to
run at 1200 rpm for 30 minutes.
Place a thermometer in the coolant
at the radiator filler cap. The tem-
perature should read a minimum of
180°F., and the gauge in the instru-
ment panel should indicate within
the normal band.
If the gauge does not indicate,
short the temperature sender unit
terminal wire to ground (ignition
switch on). Do not leave the sender
wire grounded longer than necessary
to make the test, as the gauge may
be damaged. If the gauge now indi-
cates, the sender unit is defective or
not properly sealed to the
engine.
Be
sure to use an electrically conductive
sealer. If the gauge does not indi-
cate, the gauge, the wires leading to
the gauge, or the constant voltage
regulator are at fault.
OIL PRESSURE INDICATOR
LIGHT TEST
To test the indicator light, turn on
the ignition switch. Do not
sta~t
the
engine.
The light should come on.
Start the engine. The light should go
out, indicating that the oil pressure
has built up a safe value.
To test the oil pressure switch on
the engine, turn the ignition switch
on, engine not running, the indicator
hgnt snould come on. If the indica-
tor light does not come
on,
shch"t the
terminal of the oil pressure switch
unit to ground. If the tight now
comes on, the oil pressure switch is
defective or not properly sealed to
the engine. Be sure to use electrical-
ly conductive sealer
If the light still does not come on,
the bulb is burned out or the wires
from the bulb to the ignition switch
and oil pressure switch are defective.
CHARGE INDICATOR LIGHT
TEST
.To test the charge indicator light,
turn the ignition switch on with the
engine stopped. The light should
come
on.
If
it does not, the bulb is
burned out, or the wiring to the light
is defective or there is a fault in the
alternator/regulator circuit. Remove
the wiring plug from the D+ terminal
of the Bosch alternator regulator
or the IND terminal of the Lucas
alternator regulator.
Connect a jumper lead from the
D+ or IND terminal in the cable to
earth.
The indicator light should
come
on.
If the light comes on the regulator
is at fault. If the light does not come
on the fault is in the wiring or globe
.
To check the globe and wiring
the instrument cluster surround must
be removed to gain access to the
globe
.
SPEEDOMETER TESTS
To test the odometer
accuracy,
drive the car over a measured
mile.
Speedometer
accuracy
can
be
checked by comparing the speedom-
eter in question against one known
to be accurate, while two cars are
moving at the same
speed,
or by
timing the car on a measured mile.
Page
15 24
shows the correct com-
bination of gears to use for various
rear axle and tyre size combina-
tions.
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