System Overview
The information contained within this article apply only to vehicles with Standard Heater or Manual Climate Control. For Vehicles with Electronic Climate Control, refer to "Electronic Climate Control". Heating and Air Conditioning
Information marked with an asterisk (*) is not applicable to vehicles with standard heater,
Components:
2 Engine management system*
8 Low-pressure switch*
11 Blower motor
12 Damper motor, air distribution
15 Damper motor, recirculation
16 Pressure sensor*
17 Engine temp. sensor
18 A/C relay*
19 A/C compressor*
20 Control module MCC*/STD
21 Fan rheostat
Incoming Signals:
The air conditioning system control module receives signals from the following components:
- Selected air distribution from the controls on the control panel.
- Selected recirculation from the controls on the control panel.
- If the A/C has been selected from controls on the control panel.*
- Position of the damper motor for air distribution from an in-built position sensor.
- Position of the damper motor for recirculation from an in-built position sensor.
Control Signals:
The MCC control module adjusts the following components and functions based on the incoming signals:
- The position of the damper motor for air distribution.
- The position of the damper motor for recirculation.
Outgoing Signals:
The MCC control module sends a signal, based on the incoming signals:
- indicating if the A/C compressor should run, to the engine management control system via the low-pressure switch.
Fan Control:
The speed of the blower motor is controlled manually by the fan speed selector via the fan rheostat.
Temperature Control:
Temperature control is carried out using wires between the control knobs and temperature dampers, as before.
Diagnostics:
MCC and standard heaters have a simplified diagnostic system. If the control module detects a fault it stores an error code. At the same time the indicating diode for recirculation flashes once.
Error codes are obtained from the flashing of the indicating diode for recirculation.
Error codes can be erased and damper motor self-adjustment can be initiated.
Error Indication:
If the control module detects a fault the orange recirculation diode flashes once.
The diode will also flash once every time the ignition switch is turned to the radio position (X-feeding) The control module can identity 9 different faults while holding all the error codes in memory.
As long as the control module has a supply of power (X-feeding) the error codes remain in the control module's memory until they are erased. When the ignition switch is turned to the 0 position all error codes except for one are erased (5-1-1, self-adjustment has not been performed).
If the errors remain until the next X-feeding is turned on the erased error codes are stored again.
Reading Error Codes:
Turn the ignition switch to the radio position (X-feeding) and press the recirculation switch in twice in 3 seconds to read the error codes.
Any error codes will then be flashed by means of the orange indicating diode for recirculation. The error codes consist of 3 digits, the diode is lit for 1 second, turned off for 0.5 seconds and there is a delay of 2 seconds between digits. If more than one error code is stored there is a 5 second delay between the flashing of the codes.
Erasing the Error Codes:
Once the fault has been corrected the error code can be erased by turning the ignition switch to the radio position and pressing the recirculation switch in 4 times in 3 seconds.
It is also possible to erase all the error codes except 5-1-1 by turning off X-feeding.
Table of Error Codes:
Error code Description
1-1-1 No faults have been detected by the diagnostic system
2-3-1 The air distribution damper motor position sensor has short-circuited to voltage
2-3-2 The air distribution damper motor position sensor has short-circuited to earth.
2-3-5 The recirculation damper motor position sensor has short-circuited to voltage
2-3-6 The recirculation damper motor position sensor has short-circuited to earth. Error code Description
2-4-1 Short circuit in air distribution control.
3-4-2 Air distribution damper motor has been activated for too long (seizing)
3-5-1 Recirculation damper motor has been activated for too long (seizing)
5-1-1 Self-adjustment could not be carried out
5-1-2 Battery voltage below 11.2 volt
Self-Adjustment:
The control module stores information about the end positions of the air distribution and recirculation shutters in a voltage dependent memory.
If the battery has been disconnected self-adjustment will automatically be activated when the battery is connected and the ignition switch turned to the radio position.
If a damper motor has been replaced without disconnecting the battery (30-feeding), the self-adjustment must be initiated manually for the end positions to be stored in memory.
The damper motors go to their end positions, the position sensors register the positions and the information is stored in the control module.
Damper motor self-adjustment is activated by setting the ignition switch to the radio position and pressing the recirculation switch in 3 times in 5 seconds.