Why Doesn't My Vehicle Get Warm?

Now that winter is settling in, you may be finding that your heater is not working as well as you thought. Maybe you feel like your vehicle never gets warm, or it takes a long time to heat up. Let me see if I can explain to you how the system works and then you'll know just what to look for next time you have a problem.

First of all you need to know that the coolant has a lot to do with heating the vehicle. While the coolant's job is to help cool the engine, that heat is used to heat the interior of the vehicle as well. This is why it is important to do proper maintenance on the coolant system.

Coolant/Antifreeze, should always be a 50/50 mix of coolant and water. Make sure you check the bottle when you buy it. You can now buy coolant pre-mixed. If it's pre-mixed, all you have to do is pour it in. As always, check your owner's manual to make sure that you put the proper type of coolant in your vehicle. Many manufacturers sell their own
and you must use it to prevent problems in the system and keep within warranty specifications.

Always check the coolant level to make sure that it is full. Do this by checking the coolant reservoir bottle and always add to this bottle, not the radiator. It's usually a large plastic container under the hood somewhere near the radiator. If you look in your owner's manual it should show you the location  for your vehicle.

Coolant does break down over time and must be serviced. Most manufacturers recommend a coolant flush every 30,000 miles or every 2 years, again, consult your owner's manual for your maintenance schedule.

Inside the vehicle, usually on the passenger side, there is what is known as a heater core. This is a small radiator type component that fills with coolant when you turn the heat on inside the vehicle. Many times when they go bad they leak coolant on the passenger front floor and must be replaced. When you turn the fan on it blows on the heater core and sends heat into the passenger compartment.

Let's look at a couple of reasons why you may not have heat. First of all, until the vehicle warms up, the air will be cold...just like the cold engine. I usually don't even turn the heat on until I see the temperature gauge start to move off of the cold line. If you notice that the temperature gauge seems to hover down near the cold line even after you have been driving the vehicle for a while, then you probably have a thermostat problem.


In many cases the thermostat is stuck open. This means that the engine coolant takes a long time to warm up because it is constantly circulating through the engine and the radiator. The thermostat usually remains closed until the engine warms up and then it sends the hot coolant to the radiator to cool off. Consequently, if the thermostat is stuck closed, then you usually have an overheating problem.

Another thing to check is your blower motor. You should have varying speeds, and they should all work. This blows the warm air around the cabin of the vehicle. If you turn on the heat and the fan is not blowing, always check the fuse first. You can locate the fuse by using your owner's manual. A common problem is that the fan only works on high. This usually means that you have a bad resistor and you need to replace it.

If you turn the heat on and you hear the fan blowing, but only cold air is coming out, may have a problem with a blend door. This means that even though you have the vent on heat, the door is staying closed, blocking the heat from entering the vehicle. Many of these operate off of vehicle vacuum or are computer controlled. You may need to have a technician fix this problem.

The important thing is to try and figure out what's working and what isn't. This way if you have to take your vehicle in for service you can tell them exactly what is wrong. Nobody knows your vehicle better than you. Pay attention to what's going on and get things looked at before they become bigger problems.

The only place you should have to button up and wear a scarf is outside! I hope this helps you understand your heating system a little better so that you can know what they're talking about when you take your vehicle in for service. Stay warm!


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