Dodge RAM TRUCK 1500 1995 Service Manual page 1194

14 -112 G E N E R A L D I A G N O S I S — D I E S E L E N G I N E B R
cable at the rear of the heater for corroded or dirty
connections. If resistance is now anything other than
zero (0), proceed to next step.
(4) Disconnect both cables from the intake mani­
fold heater (two nuts) (Fig. 30).
(5) Measure the resistance from each of the air
heater terminal threaded studs to a ground. The re­
sistance should be zero (0). If the ohmmeter is still
reading anything other than zero (0), replace the in­
take manifold air heater.
(6) After testing and repairing, connect battery ca­
bles to both batteries.
For removal and installation procedures, refer to
Intake Manifold Air Heater in the Diesel Engine—
Component Removal/Installation section of this
group.
INTAKE MANIFOLD AIR HEATER RELAY TEST
To test the intake manifold air heater, refer to the
previous Intake Manifold Air Heater Test.
To test the intake manifold air heater relays, refer
to the following:
(1) Disconnect both negative battery cables at both
batteries.
(2) Disconnect the four small relay trigger wires at
both relays (Fig. 31). Note position of wires before re­
moval.
(3) Disconnect the four large cables at each of the
relay terminals (four nuts—figure 31). Note position
of cables before removal.
(4) Attach an ohmmeter across two of the large
studs on one of the relays.
(5) Attach a jumper wire (+ and -) to each of the
small terminals on one of the relays. Polarity is not
important.
(6) Momentarily touch the jumper wires to the ve­
hicle battery (+ and -). The relay should click and the
ohmmeter should show a closed circuit across the
large terminals. If not, replace relay and bracket as­
sembly.
(7) Repeat the same test on the opposite relay.
(8) After testing and repairing, connect battery ca­
bles to both batteries.
For removal and installation procedures, refer to
the Diesel Engine—Component Removal/Installation
section of this group.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
TEST
To perform a complete test of this sensor and its
circuitry, refer to DRB scan tool and appropriate
Powertrain Diagnostics Procedures manual. To test
the sensor only, refer to the following:
(1) Disconnect the wire harness connector from the
intake manifold air temperature sensor. The sensor
is located on the top of the intake manifold and to
the rear of the air heater (Fig. 32).
FRONT OF ENGINE
AIR TEMPERATURE
SENSOR
SENSOR
ELECTRICAL
CONNECTOR
INTAKE
MANIFOLD
(UPPER HALF)
S H U
^ o
W N
SOLENOID^
SOLENOID ELECTRICAL
CONNECTOR
J9414-93
Fig. 32 Air Temperature Sensor Location—Diesel
SENSOR RESISTANCE (OHMS)—INTAKE
MANIFOLD AIR TEMPERATURE SENSOR
T E M P E R A T U R E
R E S I S T A N C E { O H M S }
C F
M I N mm
- 4 0
- 4 0 291,490 381,710
- 2 0 - 4 85,850 108,390
-10 14 49,250 61,430
0 32 29,330 35,990
10 50 17,990 21,810
20 68 11,370 13,610
25 77 9,120 10,880
30 86 7,370 8,750
40 104 4,900 5,750
50 122 3,330 3,880
60 140 2,310 2,670
70 158 1,630 1,870
80 176 1,170 1,340
90 194 860 970
100 212 640 720
110 230 480 540
120 248 370 410
J928D-4
(2) Test the resistance of the sensor with an input
impedance (digital) volt-ohmmeter. The resistance (as
measured across the sensor terminals) should be less
than 1340 ohms with the engine warm. Refer to the
Sensor Resistance (OHMS)—Intake Manifold Air
Temperature resistance chart. Replace the sensor if it
is not within the range of resistance specified in the
chart.