Hello, I recently purchased an August 08 MCS with which the stop/start function seems to be utterly unpredictable.
In circumstances when you would expect the stop/start to kick in, it usually doesn't......but very occasionally does from time to time.
Despite the the vehicle being low mileage (15k) I am wondering if the battery could be on the way out......with it simply not being sensed as "charged" by the engine management system. But if the battery is dodgy there is certainly no other indication.
I should note i am in the habit of driving with lights on which i suppose could affect matters. Weather has been mild. Journeys long and short.
Any suggestions or pointers to help diagnose this are appreciated.
David
Ps. OBD reveals no error codes at all.
Last edited by hernibles; Nov 29th, 2011 at 05:16 AM.
Reason: Typo
Could possibly be just a bad switch? Try pushing the button with varying levels of force and angle. Could wind up being intermittent connection. Also, try using a different key. The key battery is automatically charged when inserted but if for some reason the battery is no longer holding a charge it might not start.
I'll put the battery on charge overnight tonight and see what happens tomorrow!
BTW I had a series of 7 "old" minis in the 1970's and 80's and regard this purchase as some kind of mid-life-crisis driven decision. I have not been disappointed, and especially not with the effect the "Sport" button has.
Not a sign of any stop/start action this morning, despite 10C temperature, fully warmed up vehicle and sports mode OFF.
Interestingly this morning the battery was still taking 2 amps. I should have thought a fully charged battery would only take a trickle. Maybe there is a battery problem? More to explore.
You are aware from reading your manual that there are many reasons why stop start refuses to function.My own mini with stop/start is intermitant.Problems can include reversing off your drive way without clicking seat belt into place before moving.Also it takes a while for engine to heat up,battery level low,even air conditioning being on,short journeys,if you have the climate control on and it is away from your required temp (within a tolerance) then it will not function.
.If you take your car into a dealer and they plug it in to the diagnostic device and they find it is any one of the possible reasons listed in the manual they will charge you for the privilage of testing it.Try searching for list of reasons why it might not work,or works intermitantly on internet.There are many reasons.lights on,air conditioning turned up,temprature inside car.uses lots of sensors,if it feels an exsesive load is being put on battery it wont work just in case the engine wont restart
i should have thought that if it was a battery problem you would get a symbol on the dash board?
My major problem with mine was reversing off drive way without seat belt on.Since taking it into bmw who told me this was the problem,i now make certain seat belt is on before i move and it works well between tolerances described in manual
I find it hard to believe there is a problem with a 3 year old original equipment battery on a car that has only done 15k miles. Will go to Kwik Fit and get a test done anyhow.
Good hint on the seat belt. I am not in the habit of putting it on immediately, so will give this ago.
batteries by their nature start to decay if they drop below a certain voltage for an certain period of time,the longer they are left below that voltage the worst they become it's called sulphation..
My work takes me to a few properties miles from any road through many cattle/sheep gates, so I don't tend to put my seat belt back on after getting out for the first one - and I enjoy the BCU going demented trying to persuade me to put it back on. If they weren't so polite, a "you're taking the p**s" symbol would come on in the dash.
Stop/start is by no means the only thing that not wearing a seat belt affects - one that amuses me is that the cruise control won't work!
Well this lunchtime the Stop/Start was working! I put my seatbelt on before starting the car, headlights on and sports mode also on. Not a specially long journey and 5 degrees outside.
I think the seatbelt suggestion looks promising. Thanks.
If your stop start system cuts in as normal, ie. the engine turns off, but then restarts automatically almost immediately or within say 5-10 seconds, and you know that you have just been on a long run,and battery should be well charged etc. well I had a similar 'problem'.
The cause was traced to a faulty sensor integral to the brake booster servo unit. This links with the energy regeneration charging switch etc
This fault should show up on the dealers diagnostic.
The brake booster unit was replaced, problem solved.
Don't listen to the usual std. service reception staff guff about cold engines,external temp <6.5c deg, air con, fan on,driving lights, radio on,de da de da
As a general technical point on the battery charge level, the system will not work when the current drain drops the voltage to < 13.78v
Last edited by Seamus Not Faster; Dec 7th, 2011 at 08:51 PM.
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08 MCS Stop/start erratic? 
