Dodge ram truck 3500 1996 Service Manual page 1353

BR
FUEL SYSTEM
14 - 111
D E S C R I P T I O N AND OPERATION (Continued)
WATER-IN-FUEL SENSOR—PCM INPUT
The water-in-fuel (WIF) sensor is located at the
bottom of the fuel filter/water separator (Fig. 11).
FUEL FILTER/
WATER SEPARATOR
WATER-IN-
FUEL SENSOR
DRAIN
VALVE
J9414-90
Fig, 11 Water-in-Fuel Sensor
WAIT-TO-
START
W A R N I N G LAMP
WATER-IN-FUEL
W A R N I N G LAMP
HEAT-A/C
TEMPERATURE
CONTROL
K N O B
TRANSMISSION
TEMPERATURE
W A R N I N G LAMP J9414-63
Fig. 12 Wait-to-Start and Water-in-Fuel Warning
Lamp Location
The sensor sends an input to the powertrain con­
trol module (PCM) when it senses water i n the fuel
filter/water separator. As the water level in the filter/
separator increases, the resistance across the WIF
sensor decreases. This decrease in resistance is sent
as a signal to the PCM and compared to a high water
standard value. Once the value reaches 30 to 40 kilo-
hms, the PCM will activate the instrument panel
mounted, water-in-fuel warning lamp (Fig. 12). This
all takes place when the ignition key is initially put
in the ON position. The PCM continues to monitor
the input at the end of the intake manifold air heater
post-heat cycle.
WATER-IN-FUEL WARNING LAMP—PCM INPUT
The PCM turns the water-in-fuel indicator lamp to
the ON position i f water is detected in the fuel. The
water-in-fuel indicator lamp is located i n the instru­
ment panel (Fig. 12). The lamp will illuminate for
about two seconds each time the ignition key is ini­
tially turned to the ON position as a bulb check.
Also refer to Water-In-Fuel Sensor—PCM Input for
additional information.
AIR CONDITIONING CLUTCH RELAY—PCM
OUTPUT
The A/C relay is located in the Power Distribution
Center (PDC) (Fig. 13). Refer to label on PDC cover
for relay location.
The powertrain control module (PCM) activates the
A/C compressor through the A/C clutch relay. The
PCM regulates A/C compressor operation by switch­
ing the ground circuit for the A/C clutch relay on and
off.
The PCM will also de-energize the relay i f coolant
temperature exceeds 125°C (257°F).
POWER
DISTRIBUTION
CENTER
(PDC)
J9414-10
Fig. 13 Power Distribution Center (PDC) Location
AUTOMATIC SHUTDOWN (ASD) RELAY—PCM
OUTPUT
This circuit controls operation of the ASD relay. I t
provides the necessary power to operate the genera­
tor field control for charging system operation.
The ASD relay is located in the power distribution
center (PDC). The PDC is located in the engine com­
partment. For location of relay within the PDC, refer
to PDC cover.
GENERATOR LAMP-PCM OUTPUT
If the powertrain control module (PCM) senses a
low charging condition i n the charging system, i t will