BMW Timing Chain Repair - N47 Engine
Its personal choice of course, but we do recommend to run your air condtioning all year round, as this will help to keep the system well lubricated and sealed. You will find the use of your air conditioning in Winter helps to remove moisture from the cabin and will act as a dehumidifier, this helps to rapidly demist the windscreen and side windows during colder wet spells.
There is much to read on the internet regarding the N47 engine (March 2007 to Jan 2009), and the fact that it is prone to premature wear and tear of the chain and the surrounding guides.
If the chain or guides should fail (usually upwards of 70k mileage), this would cause the engine to effectively stop running, and may cause catestrophic consequential damage to your engine. The early warning is a quite distinct rattle on start up (from a cold engine). This rattle would usually last around 5 to 10 seconds before dissapearing, it can be hard to hear - and we're all in the habit of jumping in the car and just driving off - right?
It may be worth checking if there is an outstanding QE (Quality Enhancement) for your vehicle for this problem, but these QE's were only granted against some models.
Whilst the N47 is the main contender, there are other engine models and ages which have been known to have similar problems, but these are much less common.