Cooling fan is not working when engine reaches temp ( works fine with AC on )

[YasirE39]

Hey Guys , hope you can help me with this one.
So I just swapped the engine on an E90 328I Sedan from 2009 and now the engine is overheating due to the fan not kicking on when the coolant temp is at the spec temp think it's 92 celsius and about 200 ish Fehrinhite , codes I found when I scanned with my Maxi sys pro on the motor electronics are 1- ambient temp sensor alternator missing code I know the alternator may not be related but it's there .
now when I cut the AC on the fan turns on and work as it's supposed to and when I unplug the coolant temp sensor the fan turns to the fastest speed which I am assuming means that the CTS works fine .
I am thinking it's a faulty fan but I am going to replace the CTS today and see if that helps next I am going to replace the fan .
Please lmk if there are any other factors that may cause it to not turn on .

Day2
I replaced the Coolant temp sensor and the problem persists , I then got the old one connected it to the car while the engine is running and grabbed a lighter and heated the brass part of the sensor to see if it would activate my fan and BOOM!! the fan did kick on . now I am thinking the type of coolant in the car is not compatible and somehow not getting the sensor to heat up to temp . flushing with a none phosphate type coolant as I refuse to put a $30 plus coolant ( OEM) I red somewhere on the forums that it has to be that type of coolant so I am trying that next and will update .

I appreciate the help in advance if you have any ideas please share .
Ryan

[Saii]

Have you thought of a bad thermostat....you did an engine swap I hope you changed that

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