Heating & A/C System

HEATING AND A/C SYSTEM

System Availability
- A Manual Temperature Control (MTC) HVAC system is available in all JR series vehicles.

System Controls
The Manual Temperature Control (MTC):
- controls blower motor operation, providing four blower speeds (Low, M1, M2, & High).
- interfaces with the BCM through hardwired circuits.
- provides temperature setting information to the BCM through a resistor.
- provides an A/C request, an EBL request, and mode switch setting information to the BCM through a resistive multiplexed circuit.

The Body Control Module (BCM)
- drives the EBL status indicator in the MTC.
- drives the electric door actuators (mode, blend, recirc).
- sends and A/C request, over the PCI Bus, to the PCM when A/C operation is desired.
- uses Evaporator Temperature Sensor data to prevent evaporator freeze up while maintaining optimum cooling performance.

The MTC HVAC system uses:
- one, five-wire electric blend door actuator.
- one, five-wire electric mode door actuator.
- one, two-wire electric recirculation door actuator.

System Revisions
- The 2003 JR Manual Temperature Control (MTC) HVAC system remains carryover from 2002.

System Diagnostics
Fault detection is through stored Diagnostic Trouble Codes (DTCs)
- DTCs are displayed by the DRBIII(R)
- All MTC DTCs are stored in the BCM. Diagnostics for these DTCs can be found in the Heating & A/C category.
- DTCs pertaining to A/C compressor control circuits and the radiator fan control circuits are stored in the PCM Diagnostics for these DTCs can be found in the Powertrain Diagnostic Procedures. Diagnostics for symptoms pertaining to A/C compressor operation can also be found in the Powertrain Diagnostic Procedures.

Following A Repair
Calibrate HVAC Door Actuators
- The electric door actuators (blend, mode, recirculation) must be calibrated after making any repairs to the HVAC system. To calibrate the door actuators, either disconnect the battery or remove JB Fuse #5 for five minutes.