62A - 8
AIR CONDITIONING
Fault finding - Mode of operation62A
V4MR-372-J84-62A000$010.mif
Manual air conditioning
and
Climate controlAIR CONDITIONING
Fault finding - Mode of operation
General operation
The air conditioning system is composed of four sub-functions: heating, cold loop, passenger compartment
ventilation and user selection. Fault finding on the climate control is performed in two different ways using the
diagnostic tool.
The first procedure is by computer fault finding which makes it possible to communicate with just one computer
(select the computer concerned). The second procedure consists of performing fault finding by function which
allows communications to be established with all four computers of the AIR CONDITIONING function.
Description of the subsystems
Heating subsystem: this subsystem includes everything relating to the production of warm air in the vehicle and
management of the heated rear screen.
The main computers involved are the climate control computer (air mixing and blown air setpoint) and the UCH
(control and management of the passenger compartment heating resistors). The Protection and Switching Unit
controls the heated rear screen (and heated door mirror). The injection computer is only included in this subsystem
to supply the signals required for its management.
Cold loop subsystem: this subsystem includes everything involved in the vehicle's production of cold air.
The computers concerned are the climate control computer for air mixing, the injection computer to authorise
compressor engagement and the UPC to control the compressor and the engine fan units. On climate control
systems, the UCH merely transmits the request to engage the compressor from the climate control computer to the
injection computer.
On manual air conditioning systems, the UCH authorises or inhibits transmission of the request to engage the
compressor from the climate control computer to the injection computer depending on the status of the passenger
compartment blower (with manual air conditioning, the UCH receives and manages the passenger compartment
blower speed signal: compressor engagement is inhibited if the fan is not running).
User selection subsystem: this subsystem includes everything used to transmit the user's requests (pressing
buttons). The computers concerned are the climate control computer for climate control systems and the UCH. The
two other computers are not used for manual air conditioning.
Passenger compartment ventilation subsystem (climate control systems only): this subsystem includes
everything involved in ventilation, air mixing, air recirculation and air distribution. Therefore, only the climate control
computer is involved.
CLIM X84 1.1
Edition 2
MR-372-J84-62A000$040.mif
