Shut off the engine turning on the heater or AC. on 2003 Chevrolet Cavalier

Not all the time the engine will be turned off if I turn on the heater or Ac while the car runs. The Engine Thermostat was dianosed as opening too soon, a less than totally hot engine at best.

Your problem is??? Do you have a check engine light on? Is the car not running right?
I think it is running ok. It is a friends car and I am going to look at it more on saturday, thoughly test it check thermostat temp. and drive it. The car has a vapor emission test check engine light in the PCM.
What do you mean by a "vapor emissions test check engine light". What are the troubles codes in the PCM.
Evap Codes, gas tank leak codes not engine fuel vapor codes. When have gas tank vapor codes shut off an engine.? Becides the engine shuts off I gather, when the HVAC system, the Heat or AC is turned on. If this is true when I test the car I figure it is a network system problem. There is one of three HVAC system controlers that has a Data Link Communications system, Class 2 Serial Data type.