Dodge ram truck 3500 1996 Service Manual page 716

8W - 40 - 2
8W - 40 INSTRUMENT CLUSTER B R
D E S C R I P T I O N A N D O P E R A T I O N ( C o n t i n u e d )
VOLTMETER
Power for the voltmeter is supplied on circuit F14.
This circuit is spliced and supplies power to all the
gauges. Ground for the voltmeter is supplied on cir­
cuit Z l l .
The F14 circuit is also used to measure the voltage
level. The gauge reading changes based on the sys­
tem voltage in the F14 circuit.
TACHOMETER
The tachometer module in the instrument cluster
operates the tachometer. The Powertrain Control
Module (PCM) supplies the signal for the tachometer
on circuit G21. Circuit G21 connects to cavity C31 of
the PCM.
OIL PRESSURE GAUIE
The case grounded oil pressure sensor is a variable
resistor that connects to circuits G60 and G6. Circuit
G60 connects to the oil pressure gauge. Circuit G6
connects to the oil pressure warning lamp.
Circuit F14 connects to the instrument cluster and
supplies battery voltage.to oil pressure gauge. 'The
gauge uses two coils. One coil receives fixed current,
.circuit G60 connects the other coil to the pressure
sensor. As oil pressure changes, the variable resistor
in the sensor changes the current flow through the
second coil i n the gauge. A change i n current flow
alters the position of the gauge pointer
OIL PRESSURE WARNING LAMP
The case grounded oil pressure sensor is a variable
resistor that connects to circuits G60 and G6. Circuit
G60 connects to the oil pressure gauge. Circuit G6
connects to the oil pressure warning lamp.
Circuit F14 connects to the instrument cluster and
supplies battery voltage to oil pressure lamp.
When the oil pressure is below a predetermined
level the engine oil pressure, sensor completes a path
to ground causing the lamp to illuminate.
LOW FUEL WARNING LAMP
Circuit G4 connects the fuel level sensor to the low
fuel relay i n the instrument cluster. When the fuel
level in the fuel tank reaches a calibrated level, the
low fuel warning lamp relay illuminates the lamp.
MALFUNCTION INDICATOR LAMP (MIL)
The Powertrain Control Module (PCM) provides
ground for the M I L on circuit G3. Circuit G3 con­
nects to cavity C17 of the PCM. When illuminated,
the MIL displays the message CHECK ENGINE. For
information regarding diagnostic trouble code access
using the MIL, refer to Group 14, Fuel Systems.
IOWWASHER FLUID LAMP
Circuit G29 connects the low washer fluid switch
to the warning lamp in the instrument cluster. Cir­
cuit F14 supplies battery voltage to the lamp.
When the low washer fluid switch CLOSES, i t con­
nects circuits G29 and Z l . Circuit Z l provides a
ground path, illuminating the warning lamp. Circuit
Z l also provides ground for the windshield washer
pump motor.
HIGH-BEAM INDICATOR LAMP
Circuit G34 supplies power for the high-beam indi­
cator lamp. The ground path for the lamp is through
circuit Z3. Circuit G34 splices to circuit L3. Circuit
L3 feeds the high beam circuit of the headlamps.
TURN SIGNAL INDICATOR LAMPS
Circuits L61 and L60 power for the turn signal
indicator lamps. Circuit L61 powers the left indicator
lamp. Circuit L60 powers the right indicator lamp.
Circuit Z3 provides ground for the lamps.
ABS WARNING LAMP
ALL-WHEEL ANTILOCK BRAKES
The Controller, Antilock Brakes (CAB) provides
ground for the ABS warning lamp i n the message
center through the normally closed contacts in the
ABS warning lamp relay. When the ignition switch is
in the START position, the lamp illuminates as a
bulb test for approximately 3 to 5 seconds while the
CAB performs a system self-test. While closed, the
relay contacts complete the ground path for the ABS
warning lamp by connecting circuit G19 from the
lamp to ground on circuit Z l . Power for the lamp is
supplied by circuit F14.
If the system self-test is successfully completed,
the CAB energizes the ABS warning lamp relay by
providing ground for the. relay coil on circuit B47.
When the relay energizes, its contacts open and dis­
connect circuits G19 and Z l . Circuit A20 from fuse 14
in the fuse block supplies power to the coil side of the
relay.
Circuit G19 from the ABS warning lamp splices to
the CAB and the ABS warning lamp relay.
REAR WHEEL ANTILOCK (RWAL) BRAKES
The Controller Anti Lock Brake (CAB) provides
ground for the instrument cluster Check Antilock
warning lamp on circuit G19. Circuit F14 provides
voltage to the instrument cluster to feed the warning
lamp.
SEAT BELT INDICATOR WARNING LAMP
The seat belt indicator warning lamp is activated
by the buzzer module on circuit G13. Circuit G13