engine overheating

What is your question?

if u run the air 15 or 20 minutes it says stop car engine overheating so u stop turn it off wait 10 minutes the start it back the message goes away but the car never overheates and the air gets cold when u run it we have replaced the thermostat and the coolant is fine what do u think cause it to say its overheating when u use the air only have no problem when u run the heat