Hello forum members,

hope that this message finds you all in good health during these days of pandemic. sorry that I writing this message in English as I live in Italy and I don’t know Dutch. But I know you all understand English hence I am seeking kind answers from you.

I have a problem related to my Citroen C3 (make 2004 1.4L petrol). It started some months ago first and it always is random in nature i.e. it arrives whenever it wishes to.

As you can see in the photo, the temperature scale has reached to maximum. However, it did not arrive slowly rather it was a sudden jump from the normal 3 bar position to maximum (red bar). Initially mechanic first re-setted the internal computer memory since there were some errors of cooling fan not working and he also verified that there is as such no mechanical or physical error like leakage or liquid consumption. We also changed the coolant liquid completely just to be sure.

Then even doing about 2300 km of driving in like 10 days (even clocked 140 km/h on German autobahn), it never came but after that a normal drive at around 80 km/h it returned back. Not only this, it also came while driving within the city for less than 15 km. The mechanic again did a diagnosis and got a hint from someone that it could be the engine cooling fan resistor that was faulty. We also changed that.

Now after changing that, doing some road trips even on mountainous roads, it never came but again doing a normal city drive, the error returned.

I personally did a diagnosis that when this error comes, the air conditioning does not work at all. Like the internal fan switches on but the air conditioning does not function.

What do you guys think? A quick answer would be really really appreciated since I am planning to go back to the mechanic soon.

It’s normal that the air conditioning doesn’t work when the car thinks the engine is too hot. It is switched off to get maximum cooling capacity.

I think you water temperature sensor or the wiring to it is defective: If you create a “short” to earth on the water temp sensor the ECU thinks it is very very hot. That switches off the airco and makes the fan’s go at max speed. Since it appears “sudden” I would suspect the wiring first: If there is a bit of the insulation scraped of because the wire is touching a metal part that creates a shortcut.
Why do I suspect the wiring or sensor: If the engine runs and the temperature would be this high the cooling fluid would boil and be pushed out despite the pressure valve cap on the reservoir. You would have noticed and mentioned this for sure.

Citroensmgz schreef:

I think you water temperature sensor or the wiring to it is defective: If you create a “short” to earth on the water temp sensor the ECU thinks it is very very hot. That switches off the airco and makes the fan’s go at max speed.

I really appreciate your quick reply. Thank you very much. I already feel that I am talking to an expert

According to your statement, the fans go at max speed but I never saw the fan at maximum speed, or even working as such during these events. Even the mechanic told me that he connected with the onboard computer and his device showed that there was an error with the fan. Stopping the car and restarting it like after 10-15 min resolves the problem

I am also hoping it is just the sensor or the wires that are faulty because my mechanic suspects that the fan system might needs a replacement. What do you think?

And yes, there has not been any leakage from the reservoir regarding any boiling liquid so I am 99% sure there is no overheating of the engine.

Last hint for today:
Use an EOBD or OBD reader to read the water temperature from, the diagnostics connector. If that is “normal” i.e. anywhere between 70 and 95 degrees then it seems you dashboard unit has an issue. If the this shows your water temp is way above 100 degrees look into the sensor and the wiring.
If your fan’s don’t work at all it is logic that in city traffic you temperature goes up, if you are driving over 80 km/hour the fans don’t add to the cooling, the wind is stronger then the fans. Check this anyway.

Thank you very much for such kind and helpful replies. We are going to change the sensor and see how it bears.