Radiator fan doesn't start randomly. New fan didn't solve.

Air conditioning (not working bc there’s a leak)

A/C is inhibited if there is an engine cooling fault.


The diagram I have for fan control on a TU3/KFV early engine that also has air conditioning.


1513 is the fan 'mixer'. To control the fan which you have already changed.
PSF1 is the engine bay fuse box (BSM) and the maxi fuses.

Ok but what do these diags tell us? This engine has only the green one, I am positive about it. Could it be a thermostat problem?

The two drawings of where the sensors are will help you look to see what you have fitted there in place of a sensor and maybe find the plug for it hanging loose?

It's a very old car (2002) and potentially many previous owners. These previous owners may have made modifications or even engine swaps from a different vehicle in its lifetime. This may explain why the diagrams don't match the car. The TU3 was used in several different makes each having their own model specific features.

The electrical diagram shows you the power supplies and the signals to the fan control and these are used in conjunction with a multimeter to check supplies and signals.

The checking of supplies and signals should have been done before replacing the fan because it my not have been all down to a broken fan but rather the control system for it (sensors, plugs, sockets, fuse boxes, cables, ecu etc).

If it was mine, I would run up lexia to get the fan spinning to see that it is consistent and not intermittent.

I would also go and look to see what was fitted where the other sensor is shown on the diagram because it's not there, something must be there? Even if it is to stop the water escaping.

There is the hole where the sensor should be but it’s not there and there is no electrical plug. You can see in the diagrams you posted that the blue one should be present only until some vin number. This car was bought new in 2005, nobody touched that part. It’s simply not there.

chriz74 wrote: ↑Fri Aug 21, 2020 1:20 pm There is the hole where the sensor should be but it’s not there and there is no electrical plug. You can see in the diagrams you posted that the blue one should be present only until some vin number. This car was bought new in 2005, nobody touched that part. It’s simply not there.

You listed your car as a 2002 and that is what the information I provided is based on. It can't be new if made in 2002 and bought in 2005. It's still a 2002.
So was it made in 2002 and you bought it in 2005?

Nevertheless that sensor is not equipped on this engine. If it was simply lacking the water would flow out and it doesn’t.

Here diagram of TU3A engine without that sensor.

It is obvious that this car has engine TU3A version with just the green sensor. Anyway I will take the car at Citroen, hopefully they will find the cause of the issue. Nobody seems to know online.

chriz74 wrote: ↑Fri Aug 21, 2020 2:41 pm If it was simply lacking the water would flow out and it doesn’t.

The "blue" sensor (if fitted?) monitors the CYLINDER HEAD temperature adjacent to the number 1 combustion chamber and NOT the engine coolant temperature. It sits in a cavity that DOES NOT have engine coolant running through it. In some nomenclature it is referred to as a "coolant level sensor" but the sensor has NOTHING to do with the coolant (directly)!! However, not enough coolant in the system WILL cause the cylinder head to over heat and cause this sensor to trip!!

Something to think about:- What temperature will the COOLANT sensor indicate if there is no water in the engine while the engine is running?

But I digress, I think the whole green sensor, blue sensor is a red herring.

If you can supply your RPO number it might be helpful:- tips-for-any-citroen-c3-f8/citroen-c3-o ... -t204.html

There are three areas that I would concentrate on. First is the connector containing the wires labeled 1540B and 1599B at the engine ECU(labeled 12-- in the drawing). I will try and find out what connectors they are in. Look for corrosion on the pins at the engine ECU. I believe the wire marked 1540B is the fan speed signal wire. 1599B is the error line telling the engine ECU there is a fault. Second, Pin 14 of the 16pin grey connector in the BSM (labeled PSF1 in the drawing). Again look for corrosion on the pins of the BSM. The third is the relay inside the BSM. The relays used in the BSM and BSI are sh!t. They are not user serviceable.
I can not explain why the grey power relay (full speed) is intermittent AND the electronic speed controller doesn't work. I could explain one or the other but not both failing at the same time (because I am not familiar with the principals of operation). The signal coming from the BSM along wire number 1590B is coming through a relay and hence is only on or off. This could be a system enable line or could be a fail-safe for an engine over heat but it wont run the variable speed.
My best guess is corrosion of the pin of wire 1540B at the engine ECU. I can only assume this signal is being degraded resulting in random results?

I can’t get RPO until Monday. Anyway I am completely sure that the engine doesn’t mount the Blue Sensor or there would be the electric plug hanging and there is none. No sensor, no plug. 100% sure.

chriz74 wrote: ↑Sat Aug 22, 2020 3:38 pm I can’t get RPO until Monday. Anyway I am completely sure that the engine doesn’t mount the Blue Sensor or there would be the electric plug hanging and there is none. No sensor, no plug. 100% sure.

Forget about the blue sensor, if there was a problem the over temp light would be on all the time and I don't believe you could get a proper temperature reading from your OBDII reader.

If we have your RPO and VIN we can search for the correct circuit and parts diagram. Yes, I know, you cant do that 'till Monday.

In the mean time check the BSI and engine ECU connectors for corrosion.