Constant cooling fan
Q I am wondering if you can help me with the following. I have a 2011 Jaguar XF 3.0 Diesel. The problem is with the cooling fan constantly running when the ignition is on. The problem first appeared some 18 months ago. Turn on the ignition, without starting the engine and the fan comes on after roughly ten seconds. Turn off ignition and within 10 seconds it turns itself off. Even when the car was covered in frost, the fan would still come on, once the ignition was on, again without starting the engine.
I changed the ECT, no difference. After talking to my local garage, they advised that the most common cause of the problem was the control unit in the fan itself.
Purchased a second-hand one, and initially the fan would not come on at all! Then it started to work OK for a few months.
Guess what? It has now decided to behave exactly the same as the first fan and come on all the time! Exactly the same symptoms!
The only saving grace is the fan is not running as fast as the first one, the first one sounded like I had a helicopter above the car!
Please see pictures – there is a thick Red and Black wire to the fan, the current wires I guess. The control wires appear to be a White/blue and a Green/blue.
Any advice on what to test and look for at this plug, or any other ideas? I do not think there is a control relay for it.
Peter Wells A I would as you have done initially have replaced the engine coolant temperature sensor as this would be the most likely source of the trouble. The circuit is quite simple, and the engine control module triggers the fan control module on the information given from the ECT sensor.
The first step would be to check the wiring between the coolant temperature sensor and the ECU, as this is a two-wire system, then it may be the case that a circuit issue is the source of the trouble.
You should check the continuity of the Yellow and Brown/green wires between the ECT and the ECU and ensure the terminals are clean. If possible, reading off the temperature being registered in the ECU with diagnostic equipment would help confirm that side of the circuit is operating correctly.
The diagram I have suggests that the fan control module is triggered by a Violet wire between the fan module and the ECU, and the second wire is Grey, and this is fed from fuse 43 in the engine bay fusebox. The wires you have do not agree with the colour codes, but this circuit should also be tested.
The other consideration is that the engine cooling fan will operate if directed to do so by the air-conditioning system or if the control module suspects the DPF if over temperature, and it may be the case that the fan is being triggered due to a fault within the A/C system, or the DPF temperature sensor. These systems would be easier to fully check using a diagnostic scanner.
As you have replaced the control module with a second-hand unit and the symptoms did at first alter, it should also be considered that the replacement unit may be faulty.