Coolant shut-off valve, heater -N279
A - Bracket
B - Heater coolant shut-off valve -N279
C - Support
D - Nut
During operation of the additional water heater the engine
coolant circuit is isolated from the heating system heat exchangers in the
The isolation is effected by the coolant shut-off valve. If
no voltage is applied, the coolant shut-off valve connects the coolant circuit
between the heating system heat exchanger and the engine circuit. The shut-off
valve is activated and the heating system heat exchanger is connected to the
additional water heater. This causes the
vehicle interior to pre-heat, and not the engine.
The activation is carried out directly by the additional
heater control unit J364. On vehicles with a 4- or 6-cylinder petrol engine,
the coolant shut-off valve -N279 can also be activated with the auxiliary
heater off (for example at certain settings of the Climatronic control unit
-J255, to shut off the coolant supply to the heat exchanger of the AC unit).
Risk of scalding.
The cooling system is pressurised. The coolant
may be above 100 °C when the engine is warm.
Allow the pressure and temperature to drop as
necessary before carrying out repairs.
A Workshop Manual; Auxiliary heater; Rep.Gr. 82
A Current flow diagram