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Idle compensation

Idle compensation



From the automatic gearbox control module pin 11 the Motronic control module receives information on pin 47, if the present gear position is P-N or R-D-1-3

When one of the following gear positions R-D-1-2 or 3 is selected, the control module receives approx. 12 volts on pin 47 and thereby initiates the idle compensation.

The idle compensation is achieved when the control module opens the IAC valve so that the air flow is increased by approx. 1.8 gram/s above the normal value.

If the signal is missing, the idling speed will decrease to below 850 rpm when the DRIVE position is selected.

Radiator fan



When the Motronic control module receives information on pin 44 (from DICE) saying that the radiator fan has started, the IAC valve opens and the air flow increases to approx. 0.4 gram/s.

A/C-ACC



When the A/C-ACC is activated, either manually via the A/C-switch or automatically via the ACC-control module, the Motronic control module receives approx. 12 Volts on pin 41.

When the control module receives voltage on pin 41 the idling speed increases before the compressor is started, which is caused by the control module grounding pin 33, at the same time as relay 156 is grounded by the pressure switch.

If the signal is missing, the A/C compressor will not start.

Delay and engine speed compensation are integrated in the control module.

Idle compensation is achieved when the control module opens the IAC valve by approx. 1.4 gram/s above the normal value.

The control module always gives priority to the need of the engine to run at full power, so when top acceleration is needed, for instance when overtaking, the compressor is turned off during the time full power is needed, although for a maximum of 8 seconds.

If the coolant temperature should reach 120°C (250°F) the compressor is also stopped by the DICE (the control module for the main electronic functions) which breaks the connection to the anti-frost thermostat.