Air Conditioning Control - BMW E46 Manual

Air Conditioning control

The air conditioning system is switched on by pressing the snow flake button and having
the blower dial on position 1 or greater. The LED in the button signals that the A/C is in
stand-by.
The IHKR control module sends the following signals to the DME over the K-bus-Kombi-
CAN -bus connection:
• IHKR on stand-by (signal AC)
• Request for A/C activation (signal KO)
• Calculated compressor load
• Request for auxiliary fan
The IHKR determines the load torque for compressor activation and required auxiliary fan
speed from the pressure sensor mounted on the high side line next to the receiver dryer.
The refrigerant pressure sensor provides a voltage input signal (0-5 volts) to the IHKR. The
voltage value increases as pressure in the high side refrigerant circuit increases. The IHKR
processes this signal to determine the calculated load that will be placed on the engine
when the compressor is switched on. Pressure values that are too high or too low will
cause the compressor to be switched off.
Once all of the criteria for compressor operation have been met, the DME control module
will activate the compressor relay to energize the compressor magnetic clutch.
Control of the evaporator temperature is carried out by the IHKR signalling the DME to shut
off the compressor when the evaporator reaches the freezing point.
K-Bus: Signal AC/KO
1
0
2
IHKR
3
4
Refrigerant
Evaporator Temp.
Pressure
34
E46 Climate Control
80 3 4
100
60
2 5
120 140 1/min
100 160 x1000
120
80 180
40
6
1
60 200
12
40
11 220
0
140
20
20 240
0 7
50 30 20 15
UNLEADED GASOLINE ONLY 12
km/h
!
MPH
BRAKE ABS
miles
SERVICE
ENGINE
EML
SOON
CAN-Bus
OUTPUT
STAGE
Auxiliary
M
Fan
The IHKR cycles the compressor
o
at 1 C if the outside temperature
is above 68
KOMBI
is cycled at 3
temperature is below 68
KL30
K19 relay
Compressor
o
F. The compressor
o
C if the outside
o
F.