If you notice that it’s taking longer and longer for the inside of your vehicle to warm up on a cold day, you should get the cooling system tested. This will determine if the fan clutch needs replacing or if the thermostat is bad.
If there’s no heat in the car, there’s also no way to defrost the windows and mirrors. So, a car that takes a long time to heat up also becomes a safety concern. Just like warm weather, cold weather can put a strain on your vehicle’s components. And parts degrade or become worn out over time. Here are eight possible reasons why your car takes twenty minutes to heat up.
1. Stuck Thermostat
The most common reason why your car takes 20 minutes to heat up is due to a faulty or broken thermostat. The thermostat could be stuck open or stuck closed. This isn’t just a problem for your heating system. It’s also a problem for your engine.
A heating system consists of a heater core, heater fan, your car’s coolant system and HVAC controls. Your heater gets heat through the cooling system. The thermostat opens and closes to regulate coolant flow. But if it’s stuck open, the engine becomes overcooled, and the heater won’t work properly.
2. Heater Core Issues
Another obvious reason why your heater takes such a long time to heat up your car is because of a malfunctioning heater core. The heater core is a heat exchanger. It’s part of the air conditioning system that’s responsible for heating up the cabin and defrosting the windshield and mirrors.
The heater core is located inside the HVAC loop after the evaporator and ventilation blower. It exchanges the temperature of heat and water. When you want heat, it uses the coolant to increase cabin temperature. Contributing factors to heater core issues include age, corrosion, coolant issues and other problems we’ll get into as you keep reading.
3. Faulty Heater Valve
The heater valve controls the flow of coolant to the heater core. It’s typically located near the firewall of the engine bay. But if the valve won’t open for any reason, coolant can’t flow to the heater core, and you’re left with no heat.
Debris and corrosion are the two most common reasons why a heater valve becomes stuck in the closed position. A heater control valve is also important in cold climates to keep your engine from freezing.
In a diesel engine, a heater control valve can keep the engine from overheating. If you notice that yours has become damaged it’s necessary to replace it as soon as possible.
4. Low or Dirty Coolant
Your car’s cooling system works like a small radiator. Once the engine gets to the right temperature, it heats the coolant. The heated coolant passes to the heating core through hoses and the fan blows heat from the core into the interior of the car.
But if the coolant level is low, the heater core isn’t working, or the fan isn’t functioning properly. It can take a long time for the cabin to heat up. If the coolant is dirty with rust particles and other contaminants, it can prevent the heating core from heating the cabin properly.
5. Malfunctioning Heater Fan
But it could be that all the components above are working exactly the way they should, and the problem is with the heater fan.
A malfunction heater fan could be a mechanical or electrical issue. Also known as the blower motor, this component is responsible for pushing heated or cooled air through the dashboard vents based on the setting and fan speed of the climate control.
The blower motor resistor is responsible for adjusting the amount of current going to the blower motor based on your selected fan speed. But if the blower motor fails, only a small amount of air gets pushed through the vents which is why it can take as long as 20 minutes to heat up your car.
6. Clogged Radiator
A clogged radiator can cause all sorts of problems, including a heater that takes forever to heat your car. The most common way a heater becomes clogged is due to rust. It accumulates in the radiator over time where it remains dormant until it starts causing issues. A radiator can also become clogged if you travel through dusty or gravel roads often. If the radiator is clogged, then the coolant won’t be able to generate the heat that the heater fan needs to push hot air into the interior of the car.
7. Air Pockets in the Cooling System
Another reason why your car takes 20 minutes to heat up is because of a phenomenon known as airlock. This is when pockets of air are introduced into the cooling system. A cooling system – like many systems in a car – is a closed system. But when there’s the presence of a foreign object like air, it won’t be able to function as it should.
Airlock can cause strain on the cooling system which not only causes strain on the heating system. But strain on the performance of your vehicle. The cause of airlock can usually be traced back to a failure to maintain pressure due to a bad radiator cap.
8. Failing Water Pump
The water pump is responsible for circulating coolant throughout the engine and heater core. So, naturally if it’s not working properly, it’s difficult for heat to reach the cabin of your car.
One way to tell if your water pump is going bad is that you’ll notice a sweet smell of coolant indicating a coolant leak. You’ll also notice a puddle of coolant under your car every time you leave your parking space. While you technically can drive with a bad water pump (I’ve done it). It’s not a good idea if you can help it.