Generator (GEN) (Alternator control module (ACM))
See ALTERNATOR AND REGULATOR - DESIGN AND FUNCTION .
Scheme 208
The central electronic module (CEM) (4/56) communicates with the alternator control module (ACM) (6/26) via LIN-communication. In this way the central electronic module (CEM) receives information about how much current the generator produces and how much current can be used for the various loads in the vehicle.
The central electronic module (CEM) uses the prevailing outside temperature to calculate the voltage at which the battery should be charged.
Under certain conditions the generator cannot produce enough current for those loads which are connected. The central electronic module (CEM) communicates with the climate control module (CCM) (3/112) which then completely or partially switches off the following loads
- electrical additional heater
- rear demist
- electrically heated seats
- heated door mirrors.
The central electronic module (CEM) also transmits a request via the Control area network (CAN) to the engine control module (ECM) to increase the engine idle speed.
When the engine is not running all current is taken from the battery. There are a number of different loads which can be activated when the engine is not running, for example the infotainment system (XC90). The central electronic module (CEM) continuously monitors the voltage level of the battery. When the voltage level is too low the central electronic module (CEM) transmits information to the infotainment control module (ICM) (16/1) which then shuts off the infotainment system. In the event of a fault, the central electronic module (CEM) transmits data via the Control area network (CAN) to the driver information module (DIM) (5/1) which displays a text message to the user.
If the infotainment system used in key position II, when the engine is not running, the information is sent to the driver information module (DIM). A message is displayed if the infotainment system is switched off for 2 minutes.
Scheme 209
To charge the battery optimally the central electronic module (CEM) calculates the output voltage from the generator (GEN) using the temperature of the battery. The alternator control module (ACM) controls the output voltage, depending on the control from the central electronic module (CEM). See the illustration above. In some driving conditions for example, the engine control module (ECM) is able to affect generator (GEN) control, whereby the output voltage will deviate from the above.