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Why doesn't my Ford Fiesta's stop-start system work all the time?

I have a 2012 Ford Zetec 1.0 litre 125 EcoBoost with Stop/Start. However, it only occasionally seems to work. I asked my garage to check it at the recent service and they said it was OK. They mentioned it is dependent on battery voltage and, if other items were operating such as climate control, heating etc due to the very cold weather, I can understand the battery being under load and the heating being used, but recently with the warmer weather it still does not seem to operate regularly. Is this a fault with the Ford system?

Asked on 11 May 2013 by MP, Rustington

Answered by Honest John
No, it's not a fault. It will not switch off if there is too much load on the electrics, if the ambient temperature is too low, and if the turbo is too hot, in order to protect the turbo bearings.
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