Dodge Ram Truck 1500-2500-3500. Manual — part 2044
*BLOWER SPEED DOES NOT CORRESPOND WITH CONTROL SETTING
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HVAC - ELECTRICAL DIAGNOSTICS
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*BLOWER SPEED DOES NOT CORRESPOND WITH CONTROL SETTING (CONTINUED)
For the Manual Temperature Control circuit diagrams (Refer to 24 - HEATING & AIR CONDITIONING - SCHEMAT-
ICS AND DIAGRAMS).
For a complete wiring diagram Refer to Section 8W.
Possible Causes
(C71) BLOWER MOTOR LOW DRIVER CIRCUIT / (C73) BLOWER MOTOR M2 DRIVER CIRCUIT / (C72)
BLOWER MOTOR M1 DRIVER CIRCUIT / (C70) BLOWER MOTOR HIGH DRIVER CIRCUIT SHORTED TO
GROUND
(C71) BLOWER MOTOR LOW DRIVER CIRCUIT / (C73) BLOWER MOTOR M2 DRIVER CIRCUIT / (C72)
BLOWER MOTOR M1 DRIVER CIRCUIT / (C70) BLOWER MOTOR HIGH DRIVER CIRCUIT SHORTED TO
VOLTAGE
(C71) BLOWER MOTOR LOW DRIVER CIRCUIT / (C73) BLOWER MOTOR M2 DRIVER CIRCUIT / (C72)
BLOWER MOTOR M1 DRIVER CIRCUIT / (C70) BLOWER MOTOR HIGH DRIVER CIRCUIT SHORTED
TOGETHER
(C71) BLOWER MOTOR LOW DRIVER CIRCUIT / (C73) BLOWER MOTOR M2 DRIVER CIRCUIT / (C72)
BLOWER MOTOR M1 DRIVER CIRCUIT / (C70) BLOWER MOTOR HIGH DRIVER CIRCUIT OPEN
BLOWER MOTOR RESISTOR BLOCK OPEN
A/C HEATER CONTROL
Diagnostic Test
1.
CHECK IF THE BLOWER MOTOR RUNS WITH THE BLOWER CONTROL IN THE OFF POSITION
Turn the Blower control to the Off position.
Turn the ignition on.
Does the blower motor run?
Yes
>> Go To 2
No
>> Go To 3
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*BLOWER SPEED DOES NOT CORRESPOND WITH CONTROL SETTING (CONTINUED)
2.
CHECK THE (C71) BLOWER MOTOR LOW DRIVER CIRCUIT, THE (C73) BLOWER MOTOR M2 DRIVER
CIRCUIT, THE (C72) BLOWER MOTOR M1 DRIVER CIRCUIT, & THE (C70) BLOWER MOTOR HIGH
DRIVER CIRCUIT FOR A SHORT TO GROUND
Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Disconnect the Blower Motor Resistor Block harness connector.
Measure the resistance of the (C71) Blower Motor Low Driver circuit,
the (C73) Blower Motor M2 Driver circuit, the (C72) Blower Motor M1
Driver circuit, and the (C70) Blower Motor High Driver circuit between
ground and the A/C Heater Control C2 harness connector.
Is the resistance below 10K ohms on any of the circuits?
Yes
>> Repair all circuits with a resistance below 10K ohms for a
short to ground.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8
-
ELECTRICAL/ELECTRONIC
CONTROL
MODULES/
FRONT CONTROL MODULE - DIAGNOSIS AND TEST-
ING).
No
>> Replace the A/C Heater Control in accordance with the
Service Information.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).
3.
CHECK THE (C71) BLOWER MOTOR LOW DRIVER CIRCUIT, THE (C73) BLOWER MOTOR M2 DRIVER
CIRCUIT, THE (C72) BLOWER MOTOR M1 DRIVER CIRCUIT, & THE (C70) BLOWER MOTOR HIGH
DRIVER CIRCUIT USING A TEST LIGHT
Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Turn the ignition on.
NOTE: The test light must illuminate brightly. Compare the bright-
ness to that of a direct connection to the battery.
Using a 12-volt test light connected to ground, back probe the (C71)
Blower Motor Low Driver circuit, the (C73) Blower Motor M2 Driver cir-
cuit, the (C72) Blower Motor M1 Driver circuit, and the (C70) Blower
Motor High Driver circuit in the A/C Heater Control C2 harness con-
nector.
Does the test light illuminate brightly on each circuit?
Yes
>> Go To 4
No
>> Go To 8
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HVAC - ELECTRICAL DIAGNOSTICS
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*BLOWER SPEED DOES NOT CORRESPOND WITH CONTROL SETTING (CONTINUED)
4.
CHECK THE (C71) BLOWER MOTOR LOW DRIVER CIRCUIT, THE (C73) BLOWER MOTOR M2 DRIVER
CIRCUIT, THE (C72) BLOWER MOTOR M1 DRIVER CIRCUIT, & THE (C70) BLOWER MOTOR HIGH
DRIVER CIRCUIT FOR A SHORT TO VOLTAGE
Turn the ignition off.
Disconnect the Blower Motor Resistor Block harness connector.
Measure the voltage of the (C71) Blower Motor Low Driver circuit, the
(C73) Blower Motor M2 Driver circuit, the (C72) Blower Motor M1
Driver circuit, and the (C70) Blower Motor High Driver circuit in the A/C
Heater Control C2 harness connector.
Is there voltage present on any of the circuits?
Yes
>> Repair all circuits with voltage present for a short to volt-
age.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8
-
ELECTRICAL/ELECTRONIC
CONTROL
MODULES/
FRONT CONTROL MODULE - DIAGNOSIS AND TEST-
ING).
No
>> Go To 5
5.
CHECK THE (C71) BLOWER MOTOR LOW DRIVER CIRCUIT FOR A SHORT TO THE (C73) BLOWER
MOTOR M2 DRIVER CIRCUIT, THE (C72) BLOWER MOTOR M1 DRIVER CIRCUIT, & THE (C70) BLOWER
MOTOR HIGH DRIVER CIRCUIT
Measure the resistance between the (C71) Blower Motor Low Driver
circuit and the (C73) Blower Motor M2 Driver circuit, the (C72) Blower
Motor M1 Driver circuit, and the (C70) Blower Motor High Driver circuit
in the A/C Heater Control C2 harness connector.
Is the resistance below 10K ohms between the (C71) Blower
Motor Low Driver circuit and any of the other circuits?
Yes
>> Repair all circuits with a resistance below 10k ohms for a
short to the (C71) Blower Motor Low Driver circuit.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8
-
ELECTRICAL/ELECTRONIC
CONTROL
MODULES/
FRONT CONTROL MODULE - DIAGNOSIS AND TEST-
ING).
No
>> Go To 6
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