The Big Chill and Other Car Heater Symptoms

If you’re thinking about whether or not to get that cranky car heater fixed this winter, it’s a good idea to remember where you live. 

Although Ann Arbor’s weather is warmer than most places in Michigan, our average nighttime temperature in January is 16.5 degrees Fahrenheit. That means it’s brutally chilly when you get into your car in the morning. December is our rainiest month, with an average of 13.9 days of rain, while we average 43 inches of snow each winter.

Lake effect snow is a fact of life here, and cold temperatures help snow stay around longer. Your car must be ready to take you where you need to go – safely.  

What this means is that Mother Nature demands that we take winter seriously. You’re pushing your luck if you decide that an hour-long drive is doable without a heater, which is why Louie and John’s Complete Auto Service employs only top-notch certified technicians.

The news warns you to stock your car with a winter emergency kit (check with the American Red Cross for a suggested list of essentials), but will your car be warm enough to protect you from the elements?  

If you turn on the heater but no lovely warm air drifts out of the vents, it’s obvious that there’s a problem: you’re cold, and the heater isn’t heating! Finding out what’s gone wrong and fixing it may not be as obvious.

First things first: you need to know how your heater works to figure out what’s gone wrong. Your engine cools by water pumped through and around the engine in most cars and trucks. When prompted by the thermostat, the water picks up the engine’s heat and runs to the passenger compartment and into a small radiator called a heater core. A fan then blows warm air across the heater core and onto your feet and windshield through your defroster. 

It sounds simple enough, but it’s more complicated than that. So what could go wrong?

The heater system contains wires, controls, thermostats, pipes, and hot water; any of these could break and steal your precious heat! 

In no particular order, let’s look at all the potential problems.

Car Heater Problem 1: Low Coolant 

The same coolant that keeps your engine from overheating moves through the heater core. Start your engine and let it reach the temperature you usually see when driving (or up to halfway between C and H). Let the heater run for a minute or so – is the air getting warm? If not, you may not have enough coolant in the system. Add some, but make sure it’s combined with antifreeze. Don’t just add water. By the way, your car’s cooling system needs the correct level of coolant (water plus antifreeze) to protect the engine too.

Broken Thermostat

This critical part moves hot water to your heater core and helps move coolant through the engine. The thermostat allows hot water to move to the heater core, so if it’s not working, you won’t feel any hot air.

Car Heater Problem 3: Broken Heater Fan

You have hot coolant in the heater core, but no air is moving, or only a little is moving – now what? This one can be complicated. The heater fan switch could be broken, but maybe there’s a short circuit somewhere or you’ve blown a fuse. 

Broken Controls

Here’s another place where wiring and fuses also come into the picture. Maybe everything else is working as it should, but your controls aren’t. The problem could be a broken dial or a faulty touchscreen. Then again, sometimes it depends on the age of your vehicle.

Broken Wiring or Blown Fuses

Did we talk about fuses before? Get out your owner’s manual and find the fuse box. If the fuse for the heater or the heater fan looks like it’s blown, you can replace it – but something is causing the problem. You can’t change fuses forever. Your engine’s wiring system is a maze – you’ll need help to find a broken place.

Broken Heater Core

Broken? Clogged? Leaky? If this describes the health of your heater core, then you’ve got problems. Your heater core closely links to your radiator and the cooling system. If the radiator is rusty or if the coolant is dirty, gunk can get into your heater core and clog it. A dead heater core means no hot air. A leaky radiator can prevent coolant from reaching your heater core at all, which also means no heat – and unless you fix the radiator leak, you can kiss your heater goodbye.  

You’ve figured out that something is wrong with your heating system, and maybe you think you know what the problem is. Now what?  

Car Heater Options

You have two choices here, NOT three. Unfortunately, your first choice is to drive a cold car: bad idea. 

The heating system doesn’t only warm your body; it defrosts your windows. You MUST be able to see other drivers and the road.  

The second choice is no choice at all. There are NO other ways to heat your car. Forget any ideas you have about using a propane or electric space heater.   

Listen, winter can be scary; ask Michigan. It’s cold up here! 

Put on a heavy coat, hat, and gloves, and drive to Louie and John’s Complete Auto Service. 

Unless you are a mechanic, you’re doing your best guesswork, and that can spell bad news.

The good news is that we never guess. We get it right so you can get on with your life.