DFI AC compressor shutoff function

P07.13-0395-76

Design

A1 Instrument cluster

A9k1 Electromagnetic clutch (A/C compressor)

CAN Controller Area Network (CAN data bus)

K40 Relay module (up to 02/97)

K40/4 Fuse and relay module (as of 03/97)

L5/6 Crankshaft position sensor

N3/8 DFI control module

N19 Tempmatic air conditioning pushbutton control module

N22 Automatic A/C push-button control module

R25/2 Accelerator pedal position sensor

Task

Switching off AC compressor in order to improve engine output when starting off.

Function

The Tempmatic air conditioning pushbutton control module (N19) or Automatic air conditioning pushbutton control module (N22) receives a signal from the instrument cluster (A1) which switches the AC compressor off or on depending on engine load and speed.

AC compressor cutoff is controlled by the DFI control module (N3/8) which communicates with the instrument cluster through the CAN data bus. The AC compressor is shut off with a time delay of up to 1 second.

The AC compressor is shut off if one of the following operating states exists:

 Accelerator pedal depressed > 90 %

 Engine speed < 1050 rpm

The AC compressor is switched on if one of the following operating states exists:

 Accelerator pedal depressed < 90 %

 Engine speed > 2500 rpm