Please tell me where mentions condenser fan for engine cooling .
BMW DIESEL
3 DESCRIPTION AND OPERATION
COOLANT CIRCULATION
Operation
When the engine is started from cold, the thermostat,
integral in the housing (2), prevents any coolant
circulation through the radiator by closing off the
supply from the radiator. During the engine warm up,
the water pump (4) pumps coolant around the
cylinders in the crankcase (12) and through separate
galleries to the cylinder head. At the rear LH side of
the cylinder head, a proportion of the flow is diverted
through a heater feed pipe (7). The heater feed pipe is
connected to the heater matrix (8), which is housed in
the distribution unit of the heating and ventilation
system. This coolant is then carried, via the heater
return pipe (9) back to the water pump. The remaining
coolant flows through a bypass port at the front of the
cylinder head back to the water pump to complete the
cycle.
When normal engine running temperature is reached,
the thermostat opens and a secondary valve closes
the bypass port. With the thermostat open, coolant is
circulated through the top hose (5) to the radiator.
Coolant is drawn from the base of the radiator by the
water pump. Coolant circulation through the
crankcase and cylinder head to the heater matrix
remains the same.
An integral bleed pipe (6), connects the top of the
radiator to the expansion tank and aids bleeding of air
from the coolant system. The expansion tank cap
contains a pressure valve which allows excessive
pressure and coolant to vent to the overflow pipe (11)
if the system has been overfilled.
VISCOUS FAN
The viscous drive unit for the cooling fan on diesel
engines work on the same principal as that fitted on
V8 engines but is of slightly different size. See this
section.
Condenser fans control
The need to run the condenser fans, and the speed at
which they operate, is dependent on the pressure in
the refrigerant system, which in turn is dependent on
the amount of heat being extracted from the vehicle
interior and the ambient conditions.
When the ATC ECU energises the compressor clutch,
it simultaneously earths the line from the coil of the
condenser fans control relay. If refrigerant pressure is
sufficient to require operation of the condenser fans,
the contacts in the single pressure switch are closed,
and the condenser fans control relay energises. At
refrigerant pressures that require the condenser fans
to run at slow speed, the energised condenser fans
control relay connects the condenser fans in series,
via the LH and RH condenser fan relays, and the fans
run at slow speed.
If the refrigerant pressure increases to the upper limit
for slow speed operation of the condenser fans, the
fan speed contacts in the dual pressure switch close
and connect an earth to the coils of the LH and RH
condenser fan relays. The two condenser fan relays
then energise and connect the two condenser fans to
separate power supplies (i.e. in parallel) and the
condenser fans run at fast speed. If the refrigerant
pressure decreases to the lower limit for fast speed
operation, the fan speed contacts in the dual pressure
switch open, de-energise the condenser fan relays
and the condenser fans return to slow speed.
