Service P+us Car Care Centre
Mar 20, 2015

Why Is My Car Heater Not Heating Up?

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With the winter weather visiting us the same time each year, being without efficient heating in your vehicle is an annual concern. Fortunately, it’s not very hard to figure out why your car is refusing to heat up and leaving you in the cold. But before we talk about what can go wrong, it’s helpful to understand how your car’s heating is supposed to work.

Broken Car Heaters

In fact, the cabin of your car is warmed through the same process that keeps your engine cool: Coolant is circulated through the engine in order to absorb heat. This heat is then transferred to the cooler outside air through the radiator before the coolant circulates back into the engine.

A small portion of this coolant is directed instead through a smaller radiator responsible for heating the cabin before being exposed to the outside air and losing its heat. While this may seem like a fairly simple and reliable system, there are a few things that can go wrong.

Broken Thermostat

If the cabin of your car is simply not heating up, it is always a good idea to start your troubleshooting by checking the engine’s temperature. In order to help engines warm up quickly when they start, a thermostat controls the flow of coolant, restricting it until a specific temperature has been reached.

If this thermostat wears out, the thermal valve will not open or close properly, leading your engine to overheat or run cool. If your thermostat is the problem, check your manual to see how to replace it: in some car models it’s an easy job, while others will need to be taken to your mechanic.


If the thermostat is fine and the engine is the correct temperature, the next most likely cause of a cold cabin is a blockage in the flow of coolant. This will typically occur in the heater core and is caused by a buildup of sediment and grime between fluid changes. Flushing the system with clean tap water before refilling should correct the problem.

Low Coolant Levels

Cabin heating problems which occur intermittently may be the result of low coolant levels. In these cases it’s not uncommon to experience heating issues while the car is not moving and then find that the heating works fine once you have moved along.

Replace and check your vehicle’s fluids regularly as low fluids may cause serious damage, shortening the life of your car.

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