Changed Radio, now doesnt want to start

[i00aarnol]

Hi all, this is my first BMW so dont know a lot about them, i fitted a stereo in it, no problems. decided to change it to another then it wouldnt start. press start button but would not turn over and the TCS and ABS lights came on. it now starts but really struggles but if left overnight will not turn over on first try. also the heater controlls are making alot of noise when ignition is turned on, could this be connected? pls help as this is very frustrating!!