Heater isn't working

1 usually the coolant two lower can be like this, add some coolant can improve immediately in this situation. use a flash light to check coolant level, it should be over lower grade. don't open the cap when your engine is hot. 2 another situation, if thermostat keep open will be like this, but you can find the water warm slowly than before, and the warm wind will come really late and weak. change the thermostat is not easy for this car. 3 some block in cooling system also like this, when is your last time for full replace coolant, if it was long time ago, mechanic maybe try flush it and replace new coolant first. 1 cheap you can do it by yourself 2 some cost but you can identify this by check water temperature meter 3 it should be a regular maintaining