So, with heaters you mean glow plugs [0]. However, they are not the problem if the engine starts. If your problem is that the engine starts, but it takes a ver

So, with heaters you mean glow plugs [0]. However, they are not the problem if the engine starts. If your problem is that the engine starts, but it takes a very long time to get warm air from the heating system, in modern cars it's most likely just that the engine is extremely efficient in converting energy of fuel to kinetic energy, so there is no excess heat that could be used for heating the cabin and keeping windows clear from mist. (Heating is also slow or off if your engine is out of coolant, but if you keep running it without coolant, you'll soon break it so that you really do notice.) Just think what this heating problem will be in electric cars... [0] https://en.wikipedia.org/wiki/Glowplug https://en.wikipedia.org/wiki/Glowplug