Anyone have their engine not do the start stop when activated at a stop light?

I had that happen today. I swear I had it engaged. but the little A with the arrow around it was just greyed out. It was a hot day I thought maybe the AC exempts it from shutting the engine off to keep the AC running?
Is there any options (other than turning it off) that tell it to not do its thing?

 

Here is the link Ford's "Auto Start-Stop" video on how it works and when it doesn't. You are correct, there are several reasons that it doesn't work with different conditions of the vehicle, I think this will enlighten you.
Steve

http://owner.ford.com/how-tos/vehicl...-150&year=2015

 

perfect! Thanks!