Mazda MPV Heater doesn't work coolent level fine temp knob doesn't change temp but does change air velocity heater core hoses are only slightly different temps any ideas?
Are you checking the coolant level at the radiator or at the overflow tank? You need to check the cooling system, not the overflow tank.
If you recently changed your coolant, you may have air trapped in the cooling system. You'll need to rev the engine up and force the air out of the system. You may need to rev the engine pretty high.