is there tell tale sighns that it is not working correctly? on 2017 m8 ?

 

If they don't work correctly I guess they either don't open, or stick open. If they don't open then the starter motor will struggle to turn the engine over, as the ACRs enable a less powerful starter and battery to be used. If they stick open I reckon the engine will make quite a racket while running! I've had ACRs for ten years now and, touch wood, haven't had any problems yet.