Operation of Coolant fans. (1 Viewer)

[DandB]

Hi all I hope someone can help by telling me how the Coolant fans work in my 2014 Citroen relay Van conversion. I’ve be told that the low speed fans are not working and the local dealer is charging £700 for a new coolant fan unit. Before I part with that kind of money I want to check the circuitry as I can see that the fuse/ relay box cover has not been removed by the dealer. i have read in some other articles that the fans come on together, first in low speed then if the temperature keeps on rising they switch to high speed. However from electrical drawings that I have obtained both fans seem to operate independently from each other. Can anyone explain the general operation principle and do they also operate when the AC is switched on to draw air through the condenser. Going to check the fuses and fan relays tomorrow but it would be good to know the principle of operation in case I have to delve a bit deeper.

 

[Bessy765]

The larger fan comes on first, followed by the second one if required. It’s usually the sensor that fails. With the ignition on put a wire between two of the three contacts on the plug. One will be live the other two turn on the fans. The sensor should be near the top of the rad.

 

[pappajohn]

£700. main dealer rip off pricing.


Complete rad fan assembly

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[joka250]

Search Google for local vehicle Air conditioning specialist, most should be able to source good quality fan assembly to suit if it's not sensor or wiring fault.

 

[Sundowners]

Don't know about your van but I have found that the fan on our old van came on with A/C------ the " noisy" one was controlled by temp sensor AFAIK

 

[DandB]

Thanks Sundowners and Joka for your replies. For the benefit of others I did delve a bit deeper and unfortunately it was indeed the lower nearside fan that was faulty. It is switched on by the engine management system as the water temperature sensor resistance changes with a rise in temperature to a specific level as programmed by the engine management system. This fan is called the low speed fan and is controlled by relay TO7 and protected by fuse F7. It is the big black plug in relay. A further rise in temperature causes a further change of resistance of the sensor and this change is detected by the engine management which operates the high speed fan by relay To6 and fuse F6. TO6 is the smaller red relay beside TO7. Relays TO7, TO6, F7 and F6 are in the engine fuse box on the near side wing beside the headlamp. The headlamp has to be removed to gain access to the fuse box. The fans can be tested by removing the relays and shorting out the contact pins in the sockets of the relay and fuse mounting board with a short piece of 4 mm cable ( fan draws 25 amps ). The fans should then run. There is no need to switch on the ignition as they by pass the ignition switch. If any of the two fans do not run then confirm by testing the motor windings for resistance. This can be done from underneath the van by removing the electrical plugs at each fan. The AC also causes the fans to run when it is switched on. Why there is a difference in size of the relays I am not sure but the lower fan pulses on and off when under the control of the AC system and hence maybe it has bigger contacts to take the arcing during pulsing on and off. A new twin fan unit costs £580 + vat from the dealers but equivalent fans can be found on the net for around £200. There are different fans for different variations of the model so research carefully. Take all the usual precautions when working around the fan and under the van. Disconnect the battery when working under the van or removing the fan unit.

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