RPM goes low and engine stalls

Question

I have a problem with my Mitsubishi Lancer (1998), during hot weather and when idling or between gear shifts z RPM goes low and z engine stalls especially when z AC is on and I have to start it again

Answer 1

Idle speed is low, Check the coolant level , the idle speed actuator is dependent on the coolant level, other than that the idle speed whether this is equipt with a idle speed motor or  idle actuator is non operational