All the sensors (could be just 1 or sometimes two located by the thermostat housing and easy to change ) and the computer (ecu doesn't often go wrong ) need to be working correctly because the car is meant to regulate itself according to any climat.
Above about 60 mph and whenever the system senses the engine getting too hot the fan kicks into high speed operation mode and if everything is not working as it should you can get a major overheat and do serious engine damage, where as if the fan is on too much and 'over cooling' this would mean that the engine never gets to normal running temperature which is one degree above half way on the guage and doesn't run too well and the cars heater would not get hot enough either , a related item is the thermostat, this is a device to make sure that the car heats up quickly and gets to normal running temp, it then opens to let the coolant circulate, it is easy to change and only costs about £5 you can test the old one by putting it in water just under boiling , it should open up
Laguna Owner, August 2009
