Hi, I have an 2010 r56 n12, 2 wire cooling fan. recently the fan starts normally after it reaches temperature but it never stops unless I turn the car off which then stops. The same applies to the AC, when I command it to turn on, the fan turns on but never stops, even if I turn off the AC. I have no codes.

BTW, Water pump, Thermostat, temp sensor, radiator, condenser, fan relay, everything is ok.

When the engine temp reaches 108 Celcius, the fan starts as it should. After the temp drops to around 80 C, the fan is still on, the temp starts to climb up to 105 and stays there meanwhile the fan keeps running. everything works normally. no boiling, engine working temps normal, except the fan.

In conclusion, If the fan is turned on by either the AC or the engine temp, the fan will stay on until I stop the engine. any idea? Thank you guys

 

Did you solve your problem?

 

Yes, connect a scan tool and bring up your cooling fan command state. This way you can determine if the DME is truning on the fan relay or if you have a relay that's sticking. You might also want to check to see if you have the correct fan relay installed. Some relays are latching relays and will be "latched" in a given position based on how the circuit was designed.

 

The DME is turning on the fan at 108C or when i start te AC and the relay is a new OEM. When the car is turn off when the temperature is above 108C the fan continue running and when the temperature drop below 105C the fan stop but only when the car is not running, when the engine is running, the fan start normally but never stop because the DME always give the command to run the fan even if the temperature drop below 90C and AC is off. Sorry for my english, i speek french.

 

Check for cooling fan fault codes and other fault codes. Maybe the catalytic converter is getting too hot due to fuel in the exhaust.

 

The N12 have only one speed fan activated by a relay controlled by the DME.

 

Checking for fault codes may help you diagnose the problem.

 

No fault code is present, it's the first thing i checked.

 

Is the engine possibly running too hot due to a malfunctioning thermostat? Is the coolant level low in the reservoir?

 

The level is ok and the thermostat open and close correctly. When the temperature goes above 108 , the fan start and the temperature drop to 87 and start raising slowly because the thermostat close slowly to maintain the temperature around 106. The DME maintain the fan running until the engine is stopped. To activate the fan, the DME close the pin C13 to the ground and open the pin C13 to stop the fan. In my case, the DME maintain the pin C13 to the ground even if the condition to start the fan is not present, that's the problem. The AC start the fan and the temperature above 108 start the fan, in my case, another condition is present to maintain the fan running or the DME is faulty. I know 2 conditions to start the fan, maybe another one exist...

 

An overheated catalytic converter would also activate the fan, as shown in post #5.

 

You gave me a good lead, the problem is not the temperature of the catalyst but the pressure in the air conditioning system. The DME keeps the fan on as long as the pressure in the cooling system does not drop below 6000 hPa. Now I have to find out why the pressure rises slowly in the system as the outside temperature rises. I discovered this because this morning the temperature was cool and the fan was cycling correctly. Maybe there is a lack of gas in the air conditioning system and that is what makes it more influenced by the outside temperature...I don't know much about air conditioning.

 

What is your source for this^ information?

I believe that the DME ignores signals from the refrigerant pressure sensor when the A/C is turned off, so I'm skeptical that high refrigerant pressure is related to your fan issue.

 

I continuously measured pin 13 (fan activation) of the DME, the engine temperature and the air conditioning system pressure sensor. I noticed that the cooling fan did not automatically stop when I turned off the AC, I thought it was a delay but it was never the same, however, the fan always stopped when the pressure dropped below 6000hpa. When the outside temperature is hot, the pressure in my AC system rises above 6000hpa without me starting the AC so I tested by disconnecting the pressure sensor when the request to start the fan came from the engine temperature and the fan cycles normally according to the temperature thresholds. If I reconnect the AC pressure sensor and the pressure is higher than 6000hpa, it doesn't matter if the fan start request came from the AC or the engine temperature, the fan will not stop as long as the pressure remains higher than 6000hpa even if the engine temperature has dropped to 90C. I disconnected the sensor while waiting for an appointment to have the AC charge checked, the car is still 15 years old and the charge has never been checked. There you go!

 

Unexpected (for me) but interesting. Please keep us updated.

 

For me too! Now that I understand why the fan wouldn't stop, I'll try to figure out why the AC pressure doesn't drop below the threshold. I'll update when I find out.

 

Thanks for the useful info, I'm also experiencing the same issue with my "new to me" Mini R56 Cooper (N12), where once the fan starts, it doesn't stop until you turn the car off. I used the hidden temperature menu and saw the even with the temps in the low 90 degrees celcius, the fan is still running which was odd. I never thought that it could be tied to the A/C even if its turned off.
Did you perhaps ever figure anything more on the A/C pressure side?