I have noticed on a few occasions when the auto stop-start has been working (it doesn't always work) that the engine will cut out when stopped in heavy traffic or at traffic lights and it will then just start up again after about a minute on its own without me pressing down the clutch or doing anything. Can anyone explain why the car engine starts again after the auto stop-start has engaged?

Thank you in advance for any straight forward and helpful explanations.

 

If the system senses the battery charge is getting low (particularly if you have a high electrical load, such as air con), it will restart the car.

I've had a similar issue with my stop start, it works on and off took it to garage as it's still under warranty, all they have done is charge the battery as apparently it was running at 50% dont know what can be draining the battery? Surely it shouldn't be draining so quickly in a newish car? 

For the time being my stop start is working but I know it will not last!!

Echoing the mentiond of aircon, it can only function properly with the engine running and so if the cabin temperature is rising such that aircon is deemed necessary then the engine will be restarted.

My stop / start works perfectly well with the aircon on.

Only for a limited time; there will come a point where it has to restart the engine as the compressor doesn't run when it's off. 

1 hour ago, MJNewton said:

Only for a limited time; there will come a point where it has to restart the engine as the compressor doesn't run when it's off. 

Must admit I don't much like S/S and normally disable it when I get in the car. However, the other (hot) day I knew I would have to stop at an old style level crossing and left it operative. After what seemed years (probably about 5 mins!) the engine restarted.

Much depends on which direction I'm going - one way I can drive maybe 20 miles without slipping into neutral, the other there's a light every few yards. When I have let it operate in "normal" traffic situations, it works for maybe the first 4 or 5 sets of lights then ceases to operate. Other cars I've had with S/S have operated similarly.