Low speed radiator fan not working on Citroen C3 120 VTI

[sbdiesel]

Did you find the fault?

[Lukasds]

Hello, has anyone managed to fix this?
I have the same in citroen error codes p0691,p0695,p0494
after controlling the diagbox, the low and high speed fan does not start
but after shorting the plug with the fan resistor, the fan turns on

[NitroCharger]

Ok, no worries - but Diagbox is your best bet (although I'm not sure there may an abundant supply where you are located), Any faults with the cooling system should be documented in the BSI. You can try a generic OBD code reader, but they do not have the functionality of a dealer level tool and not all can interpret the contructor-specific codes Paul.

Best of luck though and shout if you need any other help.

Hi everyone,

I have a 2012 Citroën C3 1.4 VTi. In 2019, the ECU was updated by the dealer as part of a recall or software campaign.

Since then (or at least with the current software), I’ve noticed the engine cooling fan does not activate until the coolant temperature reaches 108°C, even under low load. Once the fan starts, it only brings the temperature down to about 105°C, then shuts off.

I'm monitoring this using the FAP OBD Android app, and I’m concerned that the thermal management logic may be too aggressive or "hot," especially considering the long-term effects on components.

I’m wondering:

Is this normal behaviour for the updated software?

Is there any way to modify the fan trigger thresholds (e.g., with Diagbox, ECU tuning, or a fan controller)?

Has anyone experienced this on their EP3/EP6 PSA engine cars after the update?

Thanks in advance for any advice or shared experience!

[AussieC3]

Excellent thread with heaps of information. I have a 2007 C3. Fan would not come on so I replaced the radiator motor relay - still did not work, so I took the fan out and tested it and to my surprise it worked. Put it back in and then the fan worked as expected, when air conditioning turned on, double speed on a 40C day. Thought all was solved, but the fan is not working at all again now after a few weeks. Tested by supplying 12V to the pin on the large connector on the relay, fan is still working just fine on its own. I noticed the fan did come on briefly, twice, when I "tapped" the relay, and I am suspecting maybe a problem with the new relay or the connector with the 4 pins that goes to the ECU. I am at the point of testing the voltages on the pins to see what's there. I want to check that pin 1550 is seeing the 12V supplied via the large connector and 1590 has 12V from it's fuse. Pins 1 and 4 1540 and 1599 look to activate the relay when grounded - is it safe to ground one at a time and see what happens or will that damage the ECU ? I wonder if anyone has solved this problem. Maybe I just got given a bad new relay and need to buy another one, but I don't want to do that before I test a few more things to ensure that signals are getting to it.

[ozvtr]

Pin 1 (1540) is low speed fan.
Pin 4 (1599) is high speed fan.
Shorting to ground won't hurt the ECU.
Pin 2 (1550) is feedback to the engine ECU showing relays have power. Power failure will stop A/C working.
Pin 3 1590 is power for the relays only.
From the engine ECU, pin 1 should go "low" (short to ground) when the coolant temp is around 100'C (or a bit higher). This might be a bit difficult to monitor or simulate.
If you remove the green connector from the coolant temp sensor, pin 4 should go low (short to ground). Normally the high speed fan would come on.

[AussieC3]

Thankyou ozvtr. After checking that correct signals and voltage were on the pins from the ECU (I only checked low speed - my OBD2 reader showed max engine coolant temp of 102C) pin 1 (went to ground) and pin 3 was +12V (14.4V with engine running). I then thought to have a closer check of the relay unit itself - I didn't even think that the new unit would be faulty as it is only a few weeks old. Sure enough, I could get the relay to click and saw continuity on the fan motor connector when I applied +12V to pin 3 and -12V to pin 4 (from a spare car battery). When I applied -12V to pin 1, nothing happened. I re-checked the old relay and had the same result. Looks like I will have to purchase another fan motor relay !

[ozvtr]

Unfortunately these days, just because it's new doesn't mean its good.