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Ford focus will not start in heat

After two repair shops telling me there is nothing wrong with my car, I’m at a loss. My car is in great condition except when it decides not to start. On hot days, if I am doing several errands I need to worry about if my car will work after the first stop. After driving for a bit, when I turn off my car and return a short while later it will not start. The car will attempt to turn over and the battery works just fine, it just won’t start. Also, another issue I think is related and connected to this is that on car trips lasting more than 15 minutes, the air conditioning will stop working. The air will blow but the cool ‘conditioning’ aspect will fail and I will be stuck with hot air blowing at me. The catch to this is that after waiting 2 hours for a tow, the driver was able to start my car on the first try, thus making the tow unnecessary. Obviously my car is not ‘perfect’ like the repair shops are telling me…please help.

Try to narrow it down to lack of spark or fuel first.
Get some starter fluid and, the next time it won’t start, spray some in the air intake. Basically, take your airfilter out and spray that starter fluid right into the opening heading towards the engine, in cas eyou don’t know what an air intake is.
If it seems like it wants to start*, you have spark so likely have a fuel delivery problem. From there, it could be a plethora of related things like the fuel injection relay, fuel pump, etc.
If it doesn’t want to start, it could be an air intake problem but it is more likely to be a spark problem. I’ve seen crank sensors do what you describe in hot weather, for instance, but it could be a bunch of other things.
At least the problem will have been narrowed down a bit.

*Note that this will likely not keep the car running but will buy you a clue as to what is wrong.