Lotus 2004 ELISE Service Notes page 259

Lotus Service Notes
Front spreader plate
Front mounting
bracket
a.c. condenser
Cooling fan
KH.5 - RADIATOR FAN & RE-CIRC. PUMP CONTROL
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. The fans will also operate at half speed
irrespective of coolant temperature if the a.c. is switched on and the compressor is running. If coolant tem-
perature 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 A117M0038F has a brown label marked YWB100800; The engine relay module A111E6024F has
a white label marked YWB100970.
Section KH
Engine cooling radiator
Page 7
Rear
mounting
bracket
Radiator
mounting
panel
p106