Heat only works when driving, but why? Many car owners have asked this question but understanding the science behind it can help to answer it. The heat coming from a car’s vents is generated by the engine and relies upon consistent driving in order for it to be effective.
Have you ever noticed how your vehicle’s heating system turns on automatically when you start driving, but won’t work if the car is stationary? It can be a bit confusing to understand why heat only works while in motion, yet fortunately, there is a scientific explanation behind it.
In this blog post, Rich’s auto service will provide an overview of why heat only works when driving and discuss the factors that contribute to the phenomena. With clear information about this subject matter, you will have a better grasp of how temperature regulation works in your vehicle and how to keep yourself warm in frigid weather.
Heat only works while driving because the heat generated is produced by the car’s engine. The engine of a car must remain running consistently in order to create enough heat to be effective. When you start driving, the engine generates enough heat for warm air to travel through the vehicle’s vents and into the cabin, providing warmth for passengers. There are a few potential reasons why a car’s heating system may only work when the car is driven:
Engine Coolant-Based Heating System
As mentioned earlier, many cars use the engine’s coolant to generate heat for the cabin. When the engine is running, the coolant circulates through the engine and the heater core, absorbing heat from the engine and warming up the cabin air. If the engine is not running, the coolant will not circulate, and the heater core will not be able to transfer heat to the cabin air.
The thermostat is Stuck Open
Another potential reason why a car’s heating system may only work while driving is if the thermostat is stuck open. A thermostat is responsible for controlling the engine temperature by regulating how much coolant flows through the engine. If the thermostat is stuck open, it will allow too much coolant to flow through the engine and not enough heat will be generated to warm the cabin air.
Faulty Water Pump
If the water pump is not working properly, it can prevent the engine from generating enough heat for the car’s heating system to work effectively. The water pump is responsible for circulating coolant through the engine and the heater core, so if it is not working correctly it will not be able to transfer heat from the engine to the cabin air.
Another potential cause of heating problems is if the heater core is clogged. The heater core is a small radiator-like device that is responsible for transferring heat from the engine coolant to the cabin air. If it is clogged, it will not be able to transfer heat from the coolant to the cabin air and thus no heat will be generated.
Coolant System May Be Airlocked
The coolant system may be airlocked, which means that trapped air is preventing the coolant from circulating through the engine and heater core. This would prevent heat from being generated by the engine and thus no warm air would be available for passengers in the cabin.
Low Coolant Level
The coolant level of your vehicle’s engine may be too low, which would prevent the engine from generating enough heat for the car’s heating system to work effectively. Low coolant levels can create air pockets in the cooling system and prevent coolant from circulating properly, resulting in limited heat generation.
Air Locked Coolant System
The coolant system may also be airlocked, which would prevent the coolant from circulating through the engine and heater core. This would prevent the engine from generating enough heat to create a warm cabin environment.
Faulty Heater Valve
The heater valve may be defective, which would prevent the engine from generating enough heat for the car’s heating system to work properly. The heater valve is responsible for controlling how much hot air is directed into the cabin and if it is not working correctly, there will not be enough hot air available for passengers in the vehicle.
Radiator Leak
The radiator may also be leaking, which would prevent the engine from generating enough heat for the car’s heating system to work effectively. If a leak has developed, it will prevent the coolant from circulating properly and thus no heat will be generated by the engine.
Faulty Blend Door Or Actuator
The blend door or actuator may be faulty. The blend door controls the amount of hot and cold air that is directed into the cabin, so if it is not working correctly it will prevent the engine from generating enough heat to warm up the cabin air. Additionally, if the actuator that controls the blend door is not functioning properly, it will not be able to open and close the blend will not be able to open and close the blend door correctly, preventing hot air from entering the cabin.
In conclusion, there are several potential causes of why a car’s heating system may only work while driving. These include coolant not circulating because the engine is not running, thermostat stuck open, faulty water pump, heater core clogged, air locked coolant system, low coolant levels, faulty heater valve, radiator leak, or a defective blend door or actuator.
How To Fix Car Heat Only Works When Driving?
In order to fix the issue of car heat only working when driving, it is important to diagnose what is causing the problem. Once the source of the issue has been identified, then appropriate repairs can be carried out in order to get your vehicle’s heating system working correctly.
The coolant System Must Be Flushed
If coolant is not circulating through the engine, then it is necessary to flush the coolant system in order to remove any airlocks or obstructions that may be present. This will ensure that the coolant can circulate freely and thus generate enough heat for the car’s heating system to work effectively.
The thermostat Must Be Replaced
Failing to replace a faulty thermostat can lead to decreased coolant circulation, resulting in insufficient heat being produced for your car’s heating system. Make sure safety and comfort is top priority by promptly replacing the thermostat if it is faulty.
The water Pump Must Be Replaced
If the water pump has failed, then it should be promptly replaced in order to ensure that coolant can circulate properly through the engine and heater core. This will allow for sufficient heat production to warm up the cabin air.
Heater Core Should Be Inspected
The heater core should also be inspected for obstructions or blockages. If the heater core is blocked, then it will prevent coolant from being able to circulate through it and thus no heat can be created. Be sure to clean or replace the heater core as necessary in order to restore proper circulation of coolant.
The heater Valve Must Be Replaced
The heater valve should also be replaced if it is faulty. The heater valve is responsible for controlling how much hot air goes into the cabin and if it is not working correctly then there will not be enough hot air available to warm up the cabin air.
The radiator Must Be Inspected And Repaired
A leaking radiator can also prevent the engine from generating enough heat for the car’s heating system to work correctly. Make sure to inspect and repair any issues with the radiator in order to ensure it is not leaking.
A faulty Blend Door Or Actuator Must Be Replaced
Finally, a faulty blend door or actuator should be replaced in order to ensure the proper amount of hot and cold air is directed into the cabin. This will restore the car’s heating system to full working capacity.
By taking the time to diagnose and repair any potential issues, you can ensure that your car’s heating system will be working correctly and providing you with sufficient heat while driving. Keeping on top of maintenance will ensure your car is running smoothly and efficiently all year round.
How Does The Car Heating System Work?
The car heating system works by circulating coolant through the engine and heater core. The coolant absorbs heat from the engine and then passes it through the heater core where it is dispersed into the cabin air, warming it up. The blend door then controls how much of this hot air enters the cabin in order to maintain a comfortable temperature inside the vehicle.
In order to ensure that the car heating system works correctly, it is important to make sure that all of the components are in good condition and functioning properly. This includes flushing the coolant system, replacing any faulty parts such as thermostats or water pumps, and ensuring that the blend door or actuator is working correctly.
How to Test a Car Heating System
Testing a car heating system can help you determine if there is a problem with the heating system that is preventing it from working properly. Here is a step-by-step guide on how to test a car heating system:
Step 1: Check The Coolant Level
The first step in testing a car heating system is to make sure that the coolant level in the engine is at the correct level. If the coolant level is too low, the heating system may not work effectively. To check the coolant level, locate the coolant overflow tank and look at the level of coolant in the tank. The coolant level should be between the “low” and “full” marks on the tank. If the level is low, add more coolant to the tank until it reaches the “full” mark.
Step 2: Start The Engine
Once you have confirmed that the coolant level is correct, start the engine and let it run for a few minutes to warm up the coolant. This will allow the heating system to work more effectively and will make it easier to identify any issues with the heating system.
Step 3: Adjust the temperature control
Next, turn the temperature control to the maximum heat setting and make sure the fan speed is on high. This will help to ensure that the heating system is working as efficiently as possible.
Step 4: Check For Hot Air
Place your hand near the air vents to check if hot air is being produced. If you don’t feel any heat, proceed to the next step.
Step 5: Check The Hoses
Look for any kinks or damage in the hoses that connect the heater core to the engine and the cabin. If you find any damage, have the hoses replaced. A damaged hose can prevent the flow of coolant and prevent the heating system from working.
Step 6: Check The Blend Door Or Actuator
If you are not getting hot air from the vents, you may have a problem with the blend door or actuator that controls the mix of hot and cold air. You can check this by listening for any clicking noises when you adjust the temperature control. If you hear a clicking noise, it may indicate that the blend door or actuator is not functioning properly and needs to be replaced.
Step 7: Check The Thermostat
The thermostat controls the flow of coolant from the engine to the heater core. To check the thermostat, locate it in the engine and feel the housing. If it is not warm, the thermostat may be stuck closed. A stuck closed thermostat can prevent the flow of coolant and prevent the heating system from working. If the thermostat is the problem, it will need to be replaced.
Step 8: Check The Heater’s Core
If the above steps do not resolve the issue, the problem may be with the heater core. To check the heater core, feel the hoses that connect to it. If one of the hoses is hot and the other is cold, the heater core may be clogged. A clogged heater core can reduce the flow of coolant and prevent the heating system from working effectively. If the heater core is the problem, it will need to be cleaned or replaced.
These are the steps to test a car heating system in detail. If you are unsure about any of these steps or if you find a problem with the heating system, it is best to have a qualified mechanic diagnose and repair the issue. By performing regular tests and maintenance on your car heating system, you can help ensure that it works properly and keeps you warm during the colder months.
How To Prevent Your Car’s Heater From Going Out In The Future?
In addition to routine maintenance, you can also take a few extra steps to protect your car’s heating system. One important thing to keep in mind is to always use high-quality coolant that is recommended for your specific make and model of car. This can help prevent rust and corrosion, and ensure that the coolant is working properly.
You should also be mindful of driving in extremely cold temperatures, as this can cause the coolant to freeze and damage the heating system. If you live in an area with harsh winters, it is a good idea to winterize your car to protect it from the cold.
Another important aspect is to regularly check the air filter, as a dirty air filter can reduce the efficiency of the heating system. Replacing the air filter regularly can help keep the heating system working at its best.
Lastly, make sure to listen to your car and pay attention to any warning signs that there may be an issue with the heating system. This can include strange noises, decreased heating power, or visible leaks. If you notice any of these signs, have a qualified mechanic diagnose and repair the issue as soon as possible to prevent further damage.
By following these tips, you can help ensure that your car’s heating system stays in good condition and works properly for years to come.
FAQs about Heat Only Works When Driving
What’s a Heater Core?
A heater core is a component of your car’s heating system that helps to regulate temperature. It consists of two hoses, one which carries coolant from the engine and one which carries hot air from the cooled coolant into the car’s interior.
What’s a Thermostat?
A thermostat is a component of your car’s heating system that helps to regulate the flow of coolant from the engine to the heater core. It is typically located in the engine and can be checked by feeling the housing. If it is not warm, this may indicate that it is stuck closed and will need to be replaced.
Is There a Fuse For The Heater In My Car?
Yes, there is typically a fuse associated with the heater in your car. This fuse should be checked first if your heater isn’t working properly. If the fuse is not blown, then other components of the heating system may need to be checked and/or replaced.
How Often Should I Check My Car’s Heater?
It is a good idea to check your car’s heater once a year, or more often if you live in an area with extremely cold temperatures. Checking the hoses and thermostats can help identify any issues before they become major problems. Additionally, replacing the air filter once a year will help ensure that your car’s heating system is working at its best.
Is It Expensive To Replace A Heater Core?
The cost of replacing a heater core can vary greatly depending on the make and model of your car. Generally, it can range anywhere between $440 and $1350. If your car’s heating system fails, it is important to have a qualified mechanic diagnose and repair the issue as soon as possible to avoid further damage.
Can I Drive My Car If The Heater Is Not Working?
You can still drive on with the condition. However, you should not do so for a long time. You may also want to check your car’s coolant levels, as an overheated engine can cause damage to other components of your vehicle. If you are having trouble keeping your car warm, it is best to have it checked out by a qualified mechanic.
What Tools Do I Need to Replace the Heater Core?
The tools necessary to replace the heater core will depend on the make and model of your car. Generally, a set of wrenches, a socket set, and pliers are all that is needed. It may also be helpful to have a manual specific to your car’s make and model as well.
Is It Safe to Drive With a Faulty Heater Core?
No, it is not safe to drive with a faulty heater core. A damaged or malfunctioning heater core can cause the engine to overheat, which can lead to serious damage and necessitate costly repairs. You should have your car checked by a qualified mechanic if you suspect that there is an issue with the heater core.
No, a coolant flush will not flush the heater core. The heater core is a separate component of your car’s heating system and should be checked and serviced as needed. If you think there may be an issue with the heater core, it’s best to have it inspected by a qualified mechanic.
Will Flush a Heater Core Fix It?
Flushing the heater core may help to remove any clogs or buildup that is causing it not to work. However, if the component itself is damaged or malfunctioning, flushing will not fix the issue and a replacement will likely be necessary. It’s best to have your car checked by a qualified mechanic if you suspect there is an issue with the heater core.
Conclusion for Heat Only Works When Driving
Heat Only Works When Driving is a common issue that can be caused by various components within the car’s heating system. The thermostat, fuse, and heater core are all components of the heating system that can cause this problem. Checking these components and replacing them as necessary will help to ensure your car is heating properly while driving.
We hope that this article has helped you learn about why your car’s heat might not work when driving and how you can quickly check for blocked vents or faulty cabin air filters. Share this post with your friends, car enthusiasts, drivers, and vehicle owner neighbors – so they can benefit from learning all about this common heating issue too.
William Moore is an automotive specialist with two decades of experience, ready to give your car the care it needs. He understands all facets of auto maintenance and repair, from oil changes to brake jobs. Working with the latest tools and technologies, he provides complete service on all makes and models of cars. With his attention to detail and commitment to quality workmanship, you can expect excellent results.
