Dodge ram truck 3500 1996 Service Manual page 1359

BR
FUEL SYSTEM 14 - 125
D I A G N O S I S A N D T E S T I N G
fContinued)
BATTERY
(LEFT SIDE)
Fig. 27 intake Manifold Mir Heater Relays
(1) With the engine not running and ambient air
temperature below 15°C (59°F), turn the ignition key-
to the ON position.
(2) The wait-to-start warning lamp will come on
and the air heater relays should click ON signaling
the start of the preheat cycle. If the engine starter
is engaged before the preheat cycle of the heat­
ers is complete, the P C M will stop the remain­
ing preheat cycle.
(3) Check for battery voltage at both air heater
terminals (Fig. 26). The heater will only be ener­
gized for 10 to 30 seconds. Refer to the following
Air Heater Cycle Chart (Fig. 28) for a time/tempera­
ture comparison. .
^ ^ ^ ^ ^
wmmmm
mmmmm
MS4CATCYCU1IME
-BNmONOHrMME
^ ^ ^ ^
KMIKMON,
Above 15°C
(59° F)
0 seconds
No
-10°Cto 15° C
(15° F to 59° F)
10 seconds
Yes
-18° C to-10° F
(0° F to 15° F)
15 seconds
Yes
Below-18° C
(0° F)
30 seconds
Yes
J9414-133
HEATER TEST
(1) Disconnect both negative battery cables at both
batteries.
(2) Lift the rubber shields from each of the cable
connectors at the intake manifold air heater (Fig. 26)
to expose the cable terminals. Do not disconnect
cable nuts.
(3) Use
an ohmmeter to test the resistance
between the cable terminal (not the mounting stud)
and a ground. The resistance should be zero (0). I f
not, inspect for corroded or dirty cable connections.
Clean or repair the connections and retest before
replacing heater. I f 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. 26).
(5) Measure the resistance from each of the air
heater terminal threaded studs to a ground. The
resistance should be zero (0). I f the ohmmeter is still
reading anything other than zero (0), replace the
intake manifold air heater elements. The heater ele­
ments are part of the intake manifold and will
require manifold replacement.
(6) After testing and repairing, connect battery
cables to both batteries.
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. 27). Note position of wires before
removal.
(3) Disconnect the four large cables at each of the
relay terminals (four nuts) (Fig. 27). 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
vehicle battery (+ and -). The relay should click and
the ohmmeter should show a closed circuit across the
large terminals. I f not, replace relay and bracket
assembly.
(7) Repeat the same test on the opposite relay.
(8) After testing and repairing, connect battery
cables to both batteries.
Fig. 28 AIR HEATER CYCLE CHART