Residual engine heat utilization function

N83.50-2037-01

Shown with code (H13) Additional heat exchanger in passenger compartment or with code (HZ7) Regulated air conditioning (Tempmatic) in passenger compartment

98/2 Temperature selection switch

98/3 Air distribution switch

S98 Air conditioning operating module

S98s1 Blower switch

S98s4 EC and residual heat system button

The engine residual heat utilization makes it possible to heat the vehicle in the event of "Circuit 15 OFF" for a period of 30 min. The residual engine heat utilization system (REST) uses the residual heat of the engine for this purpose.

Activation

The REST is activated via the EC and residual heat system button (S98s4). Activation of the REST is indicated by an illuminated red light emitting diode (LED) in the EC and residual heat system button (S98s4). After the activation, the air conditioning operating module (S98) regulates the following components dependent upon the position of the temperature selector switch (98/2) integrated in the air conditioning operating module (S98):

 Coolant circulation pump (M13/5)

 Water valve (Y19/2) via water valve relay (Y19/2k1)

 Blending air flap actuator motor (M16/8)

 Blower motor (M2)

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The coolant circulation pump (M13/5) ensures that the coolant is circulated. The water valve relay (Y19/2k1) determines the flow rate of the coolant through the front heater heat exchanger using the water valve (Y19/2). The blending air flap actuator motor (M16/8) adjusts the blending air and shutoff valve thus regulating the air flow which blows by the front heat exchanger. The blower motor (M2) delivers the heated air from the A/C housing, dependent upon the position of the air distribution switch (98/3) integrated in the air conditioning operating module (S98), via the air outlets to the vehicle interior.

 Blower motor (M2) is always operated in stage 1, even if blower switch (S98s1) integrated in air conditioning operating module (S98) is set to another position.

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 When the temperature selector switch (98/2) integrated in the air conditioning operating module (S98) is set to "maximum cooling", the temperature selector switch (98/2) is turned all the way to the left into the detent position, the temperature is regulated to approx. 18 °C.

Deactivation

The REST is deactivated if of one of the following states applies:

 The EC and residual heat system button (S98s4) is pressed again.

 The status "circuit 15 ON" (ignition on) is activated.

 After expiration of an operating time of 30 min

 The battery voltage drops below 11.5 V.