I have a 2010 turbo that im pulling my hear out over. First...i keep getting p0128 thermo not up to temp code. I replaced the thermo housing and temp sensor. Filled with zerex g-05 and blead system. Temp get up at idle but thats it. Once start driving temp drops to max of 136f. Outside temp this morning was 70 degrees f. Car just will not maintain correct temp. As far as cooling fan. High speed kicks on at abt 230f and cools motor at idle. Low speed fan never comes on.....also dont come on when ac is switched on. I did test the fan by running a hot wire to the low speed side and it works. As well as the high speed fan working. I checked relay and its functioning as it should. Lastly when i turn ac on the compressor will not engage. No power to compressor. I have done some research and found that the white wire coming out pf the passenger side fuse panel is for the compressor....i have no power coming out of it......but if I tap a wire into it and plug it into a power source. The compressor kicks on.....can someone please help point me in right direction. Cars a 2010 with 85k miles

 

So you have two issues:

1-Thermostat related:
the fact that when you drive, the temp goes down makes me believe the thermostat is stuck open. did you plug the hoses the right way?
https://www.realoem.com/bmw/enUS/sho...diagId=64_1593
https://www.realoem.com/bmw/enUS/sho...diagId=17_0393

2- AC compressor related:
Usually the compressor wont kick until the pressure sensor triggers is. You might be low on freon, that's all.

 

As far as the hoses. They are all correct. The ac i did find a broken wire coming out of the plug for the low pressure sensor. I tried using a test light to c if it was getting power. And when I touched the one wire ( there are 3) it killed the motor. Freon was charged at a dealership

 

I am a radiator service support position fanatic. And have found that I sometimes leave the connection to the AC compressor unplugged after closing the car up to it's normal position.