Automatic air conditioning (AUTO A/C), function

S83.30-2016-06

Control wiring diagram
Automatic air conditioning
Inputs

1 Circuit 15

2 Circuit 31

4 Temperature control (S24.3)

6 Outdoor temperature sensor for air conditioning (B38)

7 Air outlet temperature sensor (B28)

8 Passenger compartment temperature sensor (B34)

9 Evaporator temperature sensor (B29)

11 Air conditioning switch (S95)

12 Gasoline/diesel coding

14 Compressor speed signal for 10PA15C

16 Engine speed signal

Outputs

3 Air conditioning cycle valve (Y37)

5 Temperature control (S24.3)

10 Idle speed increase (LDA)

15 A/C compressor relay (K31)

17 Compressor speed signal

18 Engine speed signal

13 Not used

A14 Automatic air conditioning control module (KLA)

B77 High/low pressure switch for air conditioning

M40m45 Heater blower motor

Y38 Electro-magnetic clutch for A/C compressor

For control of the interior temperature the automatic air conditioning control module (A14) compares the actual interior temperature with the temperature set on the temperature control (S24.3). The resulting difference is used as a reference value for the cycle time for the air conditioning cycle valve (Y37). Fine control is accomplished by comparing with the ambient temperature measured by the outdoor temperature sensor for air conditioning (B38).

To ensure that the interior temperature remains constant while driving the interference variables which occur as a result of variation in the engine speed, are recognized by the air outlet temperature sensor (B28) and the system is deregulated. If the temperature surrounding one of these temperature sensors

increases, the electrical resistance of the sensor decreases (NTC resistors).

The presence of ground potential at pin 12 indicates to the control module that the system is operating in a gasoline vehicle. If the engine speed decreases after the A/C compressor is switched on, the signal to increase the idle speed is sent to the engine control module.

Model 10PA15C speed recognition

On model 10PA15C A/C compressors the speed of the A/C compressor is compared continuously with the engine speed. A difference in the speed is recognized as slip and the electro-magnetic clutch releases the A/C compressor (Y38).