For you Mini experts. It's 2015 Countryman S, 54,000 miles, the cooling began running constantly. The engine can be dead cold over night, as soon as you start the engine the fan is on. As a matter of fact it will start just pushing the start button without actually starting the engine. Once the car is shutdown it will shutdown 6 minutes later. The only code it shows a PO128 code, low coolant temperature, low temperature is not supposed to start the fan, high is. It has no coolant leak, the system is full and I drove it 1000 miles at 70-75 MPH with the A/C on. It runs as normal. It's been in the shop for 3 days and they haven't called to tell me they found the problem. Searched the internet and could not find any mention of a similar problem.

 

Problem was a failing battery causing voltage spikes. The battery was replaced and code cleared.

 

This resolution (failing battery) doesn't seem to make sense to me but hey- I have learned to throw out traditional automotive troubleshooting strategy because -it's a Mini. Hmmmph.

I am having identical symptoms with my 2013 R60 and as I consider M Buttanic's testimony, I will monitor my battery voltage. I am reluctant to simply replace the battery at this point, but winter is coming and having a charged 12v battery waiting in the wings is not a bad idea.

Other resolutions have mentioned correcting suspicious connections in the sensor wires, so I suppose this failing battery diagnosis could be equally likely.

Onward!

 

Turned out it wasn't the battery it was the thermostat. It was sticking and causing the engine to run cool. Seems any time the temperature is out of range, high or low the computer defaults to constant fan on. Good luck, about $800 fix at the dealer. I replaced it myself, $135 for the thermostat and $30 for the special hose clamp tool needed.. Also 10 hours, some blood and cursing, I hate front wheel drive cars.

 

now THIS shows the value of participating (with a user account) in forums like these. Thanks, Buttanic! I was ready to buy a battery before I needed to (I may still though, if I see a good sale somewhere).

About this thermostat- did you get one with the sensor that needs a new wiring harness adapter? Or...?

Thanks again

 

If I recall correctly it was direct plug in.
The way I found the problem was using the Repair Solution 2 app and OBS dongle which has real time monitoring of engine instruments. I watched engine coolant temperature while driving and found the thermostat would intermittently stick open setting a low coolant temperature code.
Once the code is set the fan will stay on. If the code is reset the fan will operate normally until the next time the thermostat sticks open and set the low temperature code.