no heat on 2005 Pontiac Grand Prix

yesturday my heater just quit blowing out hot air,would it be the thermastat?its like the air conditioner is on,or would it be something else?the car isnt over heating????????
thanks!!!!

Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
1 answer
check your coolant level.
could be thermostat
heater core could have a restriction

Roy