Lotus 2004 Eleven Service Notes page 450

Lotus Service Notes
PL.3 - COOLING FANS & RE-CIRCULATION PUMP
The two cooling fans are fitted beneath the radiator or (with a.c.) condenser/radiator package, and the
coolant re-circulation pump is mounted below the header tank. Both the fans and pump are controlled by the
engine management ECU using data provided by the engine coolant temperature sensor mounted in the back
of the cylinder head.
The cooling fans are switched as a pair, and will operate at half speed (connected in series) when coolant
temperature reaches 98°C on rise, and switch off at 94°C on fall. If coolant temperature rises to 103°C, the
fans will switch to full speed (connected in parallel), reverting to half speed at 98°C.
The fans will also run at half speed, unless high coolant temperature dictates otherwise, when the a.c. is
switched on and the compressor is running, or if the engine management system detects a fault with the inlet
air temperature or coolant temperature circuits.
At road speeds in excess of 85 mph (135 km/h), equating to the fan stall speed, all fan functions are
switched off.
Heat Soak
In order to help control engine temperature after switching off an engine whose temperature is over 88°C,
the ECU will remain powered for a period of 20 minutes to allow heat soak management.
A coolant re-circulation electric pump is mounted below the coolant header tank and is plumbed into the
heater supply line. When energised, the pump circulates coolant through the engine and heater system,
drawing coolant from the back of the cylinder head, and pumping it through the heater matrix to the heater
return pipe and back into the thermostat housing. The pump functions only with ignition off in conditions where
the ECU remains live. The pump is then activated at coolant temperatures over 110°C, switching off at 100°C
on fall. If temperature should rise to 115°C, the pump will be supplemented by the two cooling fans running at
half speed, switching off at 110°C on fall.
Fan Control Module
The cooling fans, re-circ. pump and a.c. compressor are controlled by a relay module mounted to the top
of the passenger side wheelarch liner. Important Note: The a.c. relay module is identical in appearance to the
engine relay module, but the function of the two modules is different and they must not be transposed. The a.c.
relay module B117M0038F has a purple label marked YWB100801 and a blue connector moulding; The
engine relay module A111E6024F has a white or brown label marked YWB100970 and a black connector
moulding. If necessary, use a scalpal blade to slim the centre spigot of a new module connector housing to
allow its fitment on an earlier car.
If the ECU receives a coolant temperature sensor signal voltage outside of the acceptable range, a
default setting equating to 60°C will be substituted, and the cooling fans activated at half speed as an engine
protection strategy.
Note that a blockage in the a.c. system may result in the cooling fans running at full speed.
Section PL
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