Low speed radiator fan not working on Citroen C3 120 VTI

[blakey88]

Hi,

It seems my low speed fan on my Citroen C3 1.6 120 VTI 2012 doesn't come on, as I read the OBD coolant temp at around 97c, I even got to 102c (I think the high speed is working, but haven't seen it in action,
just that I never overheat, and the temp drops at around 105c in the OBD sensor reading).

To test the fan, I removed the 2 pin plug from the resistor/relay unit pictured above, and shorted the 2 pins, the fan started, so it is ok
I tested the resistor/relay unit on another friends car, and his low speed continued to work so this unit seems ok.

So what else can I check?
Is the ECU only one controlling this? Is the ecu directly wired to the 4 pins?
Is there another temp sensor but the one on the thermostat housing? If so, which one is reported on the OBD?

And about this relay:
Is this unit just a relay that connects the resistor in series to the 2 pins? What are the 4 pins pin outs?
Can it short it as well - high speed mode or is that another relay? If so where's the high speed relay?

Thanks ahead,
Paul.

[GiveMeABreak]

Pop up your VIN and I’ll check it later to get the exact temp when it kicks in on this model. There is only one fan, but can be either a single or dual speed depending on specs, but I can check which you have from the VIN.

[blakey88]

Pop up your VIN and I’ll check it later to get the exact temp when it kicks in on this model. There is only one fan, but can be either a single or dual speed depending on specs, but I can check which you have from the VIN.

Thanks! My VIN is VF7**************[VIN obfuscated, can be read by forum staff].

[GiveMeABreak]

A lot of the cooling function is automatically done within the cooling circuit by restricting or allowing flow of the coolant to the cooling radiator

Coolant temperature - Engine Running

• The engine management ECU activates the slow speed of the fans when the engine coolant temperature reaches 97 °C.
• The cooling fan stops when the engine coolant temperature comes below 92°C.
• The engine management ECU activates the fast speed of the fans when the engine coolant temperature reaches 105 °C.
• The cooling fan returns to slow speed when the engine coolant temperature comes below 100°C.

In Relation to the Air Conditioning:

• The activation of the first speed of the fan is controlled for a pressure of the air-conditioned circuit above 9,1 bars (The fan unit is cut when the pressure is below 7 bars).
• The activation of the second speed of the fan is controlled for a pressure of the air-conditioned circuit above 16,1 bars (The second speed of the fan is cut when the pressure is below 13 bars).

So unless you are getting specific warnings on the dash about the coolant, I would leave it.

[blakey88]

Thanks a lot!

Why you say I can leave it? is it because the high speed works? I just never pushed it much, no long drives (< 5km most days and sometimes 20km),
and for now I run with OBD sensor and use the heating to dissipate heat above 90c. I'll try without the heating on to see if it overheats past 105.

Is temp 100-105 ok to run at regularly?
Wouldn't it cause excessive pressure in the coolant system? (I already replaced a radiator for cracked plastic).

Regarding air conditioning, do you mean the fan on the coolant radiator?

And the other questions?

Thanks again.

[GiveMeABreak]

The fan (1510) is controlled by the Fan Assembly ECU (1529). Both speeds are controlled by the Engine ECU (1320).

The fan ECU gets power from the engine fuse box (PSF1) via Maxi Fuse 1

Pins 1, 2 & 4 are connected to the engine ECU. 1540A is Fan control (1), 1550A is Fan Control (2) and 1599A is the Fan Diagnostic Info.

So you should have a fault code if there are any issues, assuming you have a proper diagnostic tool (Diagbox is recommended).

Yes I was referring to the A/C - the fan will come on whenever the A/C is in use anyway.

[blakey88]

Finally! the correct schematic All I found online were older or different designs. Thanks a lot!

So the relay/resistor unit (1529) has two relays, both the high (pins 3-4 energized) and low speed (pins 3-1 energized).
Pin 2 (1550A) seems to be a feedback back to the ECU, that ones of the relay are closed, did you mean this is the Fan diagnostic not 1599A?
What the function of 1590A wire? Why is it connected to fuse box via some chip and what is E159? can I assume it works and has some constant potential (GND or 12v) and pin 4 and 1 control the fans - if high speed works, since it's shared with both.


According to this schematic, and my test of the 1529 unit in another car (low speed works) and assuming high speed works, seems like either 1540A wire is broken, or the engine ECU (1320) doesn't properly energize it.
Is there a guide how to disassemble the ecu cover so I can test continuity? (EDIT: ok by visual inspection, you remove the 2 plastic clips for the upper cover, then the whole unit can be lifted up with it's side cover, then disconnecting the ~3 plugs).

[GiveMeABreak]

1510 is the actual FAN not the relay.

1529 is the Fan Assembly ECU which contains the relays.

• 1599A: Fan unit diagnostic info
• 1590: Fan unit relay power supply
• 1550: fan control 2 (-)
• 1540: fan control 1 (-)
• 1589: Fan unit module power supply

1510: Fan

• 1587: left fan assembly supply

E159 in an equipotential crimped wire, as can be seen here (E159) on the diagram below.

I would be VERY cautious about dismantling the engine ECU - anything goes adrift there and you risk the car not starting. There are no instructions on disassembling these I'm afraid - that's what the diagnostic tools are for to determine any faults reported by the engine ECU. I doubt there is anything you can do inside it and I really wouldn't recommend you do, these are very sensitive.

[blakey88]

Thanks for the extra info!

Does fan control 1/2 (-) means it supplying low voltage (GND) to the relay?
So, should I test continuity with ECU plugged it?

Regarding the naming again, how is pin 4 on the Fan control unit (1529):

1599A: Fan unit diagnostic info

?

I mean it's only connected to the the high speed relay unless they sample both ? It's just that pins 1 and 4 seems symmetrical in controlling both relays.
While pin 2 seems to sample the relays status from the big pins 1 and 2 if the relays close.

[GiveMeABreak]

Here's the full part of the schematic relating to the Cooling System for you.
12A6: coolant outlet housing

The Diagnostic probably just informs the Engine ECU whether the Fan is working at single or double speed when commanded to do so.

[blakey88]

Thanks a lot.

Regarding 12A6, is that a resistive coolant temp sensor on pins 3-4? and pins 1-2 a thermoswitch? Is that on the thermostat housing, I've seen the 2 pin green one, where is the other?
Both seem like input the ECU for coolant temp, just that switchlike sensor, affects motor 1553.
So if the OBD reads a seemingly correct value, this resistive temp sensor (ECT) is probably ok.

Now that I see the whole picture, 12v is constant supplied via the max fuse MF1 to the fan relay/resistor control unit (1529) on big plug pin 2, and is what I read via the multi meter.
This 12v is switched via 2 relays inside this unit, either though a resistor or straight through.
Slow speed fan is done by energizing small plug pins 1,3 on the relay control unit. This two pins go direct to the ECU on pins 13,26 on plug 53V NR.

[GiveMeABreak]

1553 is the engine coolant pump disengagement actuator.

1357 is the Engine Coolant Temperature Earth
401 is the Coolant Temperature Signal

Yes Pin 4 on 12A6 is a thermistor

1582 is a disengagable coolant pump supply &
1570 is a controlled thermostat control.

[blakey88]

OK I verified the high speed kicked in at around 105 °C, I was in idle reving the engine and it dropped to about 90 °C and I saw the fan running what seems like fast speed.
I'm not sure if the slow speed worked on the way back to 90 °C as it slowed down slowly. I'll have to check again another time.

Thanks Marc, I'll think of how to check the ECU for continuity without unplugging it.

[GiveMeABreak]

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.

[mleppis62]

HI,

Does anybody have information what kind of volts should come to the 1529 on cables 1540A and 1550A.

I get the following
Power on (engine not running)
1540A 3.5V
1550A 1.3V (this I am suspecting to be wrong?)
1590A ~12V
1599A ~12V

Mikko