Engine Coolant light
Engine coolant light came on while driving with heater on in mid teen temperature. Turned off heater and light went out. I pulled car over and waited for engine to cool off. Checked under hood and coolant is full.
Could be small leak and some air in the system. Pressure test system and see if there is drop down on the pressure.
Could this cause the heater to not work properly???
Yes if there is air trapped in the system it will effect your cooling for the engine and the heater core would not be efficient either. You should check the coolant level when cold at the fill line. There should be two one at hot and one for cold. If the pressure test is done and it holds pressure your either looking at a restriction in the system, low coolant or air. It may be a good idea to flush the system, install a new thermostat and inspect all your hoses if that has not been done within the past couple of years.