I noticed my cooling system mode has been coming on lately and now I turned on the heat full blast and no heat is coming out. Has my thermostat gone bad? please help I need to get this fixed tonight

 

Check the coolant level first...If its low, you may not have any coolant reaching the heater core

 

Could be a stuck thermostat, could be out of coolant, so check your coolant level as step #1.

If the coolant is low, or the recovery bottle is empty, your losing it or using it. Look for obvious leaks under the vehicle, check your oil, if it looks like chocolate milk....you have an internal leak like a cracked head or blown head gasket.

Since you asked about the thermostat, here's a "How To" thread on replacing it.(2.2, 2.4, 2.0 engines).

https://www.chevyhhr.net/forums/how-tutorial-library-21/how-save-%24350-00-thermostat-replacement-2-4l-p0128-24493/

Welcome to the forum.

 

Acouple days ago it was low on coolant so i added more.i checked it this time and its fine.thats why im thinking the thermo is stuck open.heat wont blow hot now either

 

If it was low before, you need to find out why. There may be air bubbles in the system now still causing trouble too.

 

If the bottle was empty, you better check under the pressure cap. Be sure the hose is full. If the t-stat was stuck open you would get a CEL.