07 Chevy Malibu Max 6 cylinder 4.3 Lt. The temperature gauge inside car works sometimes. I hit a bump it will come on then go out. N now I have cool to warm air blowing out of vents. If I step on gas peddle then warmer air comes out. Is it clogged or heater core bad or what.
It is hard to say without knowing the engine temp. Check and replace the temp sending unit if needed. Then you will know if the engine is getting to a normal operating temp. If it isn't, that is why you have little heat. You may need a new thermostat. Also, check to make sure the coolant level is full.