[Kokolin]

Hi everyone, I hope you can help me because everyone is baffled by this!

I have a 2006 e92 335i with an n54(if that matters at all).
It has developed a really weird heater fan issue a few months ago and I don't know how to fix it, and it's getting urgent since it's raining all the time and frost will become a problem rather soon.

The fan/resistor died, I ordered new ones to change out but in the meantime, BMW sent out a letter about a safety recall(something to do with fan wires melting and causing a fire)-so the car went into BMW to get the safety recall work done.

Once BMW gave me the car back, I changed the FSR and fan itself in hopes of that fixing the issue but it didn't and here I am months later, scratching my head.
The fan works with the key in the ignition slot and ignition turned ON, but the second I switch the actual engine ON, the fan stops working.
I have been to an auto electrician, who said the wires, fan and FSR are fine, and he believes it could be the climate control panel shorting out-so I bought a new one and changed it out, nothing changed.

TLDR: Heater fan(regardless of setting or AC) works with ignition ON, but shuts off when the engine starts.

Any help and ideas would be appreciated, thank you!