RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
System Controls
The A/C-Heater Control Module:
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is fully addressable with the DRB III.
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communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
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uses input from the evaporator temperature sensor to prevent evaporator freeze up while maintaining optimum cooling performance.
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provides an A/C request to the Powertrain Control Module (PCM) over the PCI Bus when compressor operation is desired.
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controls blower motor operation, providing four blower speeds (Low, M1, M2, & High).
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controls heated mirror operation.
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controls electronic door actuator operation. A simplified control system for operation of the mode, recirculation, and temperature control actuators
provides positive positioning without the complexity of feedback from position sensors. The A/C - Heater Control Module knows the number of
operating actuator revolutions required for full door travel as well as the number of actuator commutator pulses per revolution. Using these
parameters, the A/C - Heater Control Module runs the actuator for the number of commutator pulses that correspond to the desired door position. To
maintain accuracy, the system recalibrates itself periodically at known zero and full travel conditions.
The Single-Zone HVAC system uses:
one, two-wire electronic blend door actuator.
two, two-wire electronic mode door actuators.
one, two-wire electronic recirculation door actuator.
The Dual-Zone HVAC system uses:
two, two-wire electronic blend door actuators.
two, two-wire electronic mode door actuators.
one, two-wire electronic recirculation door actuator.
System Diagnostics
Fault detection is through active and stored Diagnostic Trouble Codes (DTC's)
DTC's are displayed by the DRB III.
Active DTC's are those which currently exist in the system. The condition causing the fault must be repaired in order to clear this type of DTC.
Stored DTC's are those which occurred in the system since the A/C-Heater Control Module received the last "clear diagnostic info" message.
The A/C Cooldown Test:
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Is actuated with the DRB III.
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checks A/C system performance based on evaporator temperature sensor input.
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will not run if ambient temperature is below 12.7° C (55° F).
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will pass if the evaporator temperature drops 6.7° C (20° F) within two minutes of starting the test.
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faults display on the DRB III as test messages only after running the test.
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faults will not display on the DRB III as Diagnostic Trouble Codes.
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will cause the A/C mode switch status indicator to flash while the test is running.
If the test fails, the status indicator will continue to flash until the test returns passed. It will also prevent the EBL mode switch status indicator from
indicating EBL operating status. However, the EBL mode switch will continue to function in this state.
The EVAC Door Recalibration function:
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is actuated with the DRB III.
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monitors for faults on the actuator circuits.
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faults display on the DRB III as test messages only after running the test.
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faults will not display on the DRB III as Diagnostic Trouble Codes.
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will cause the EBL mode switch status indicator to flash while the test is running.
If the test fails, the status indicator will continue to flash until the test returns passed. It will also prevent the A/C mode switch status indicator from
indicating A/C operating status. However, the A/C mode switch will continue to function in this state.
The Actuator Circuit Test:
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is actuated with the DRB III.
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monitors for faults on the actuator circuits.
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allows service to easily diagnose and troubleshoot up to three simultaneous shorts.
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supplements the continuous diagnostics on the actuator drive system.
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faults display on the DRB III as test messages only after running the test.
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faults will not display on the DRB III as Diagnostic Trouble Codes.
