Posted 04 August 2018 - 05:36 PM
When the Aircon is OFF the fan will be switched ON by the BSI when it receives an input from the temp sensor. If the car is moving then the fan will run at low speed, if you come to a halt and the temp rises then the second triggered then the second will come into use.
With the Aircon ON the fan will start immediately or after a very short delay. It runs at low speed. This is to ensure that air is drawn through the Aircon condenser rad that is co-located with the car coolant rad. If the fan doesn't run when the Aircon is ON then it will trip the system off as a safety measure.
If when driving with the Aircon ON, the engine temp rises and triggers the fan it will run at high speed.
17 Reg C3 Saloon Flair 1.2 110BHP
Previous Xsara Picasso 20HDi, C3 SX 1.4HDi, C3 SX 1.6HDI, C4 Picasso 1.6HDi VTR+ EGS 62 Reg C3 Picasso VTR+ 1.6 HDi 92BHP