When the AC is on, it overloads the engine. So, the engine should normally overheat if the air conditioner is on. But in some cases, the engine overheats when the AC is off. It seems mysterious, doesn’t it?
So, the car overheats when the AC is off: what are the reasons? If your car overheats when the AC is off, the blower fan may be faulty. Bad thermostats, low coolant levels, air bubbles, etc., can also cause this problem.
Let’s know the reasons in detail and see how to troubleshoot the car overheating problem when the AC is off.
Car Overheats When AC Is Off: Detailed Reasons and Solutions
I will explain each reason for the problem and guide you on how to solve the problem.
1. The Blower Fan Is Faulty
When the heater is turned on, both radiator fans and blower fans work together. They should also run properly if the air conditioner is off. But if there is a fault in the blower fan, it will cause the car to overheat.
The blower fan can have physical damage that prevents the fan from running. Also, a blown fuse or wiring problem can cause the blower fan to malfunction. In that case, the engine heat won’t be dissipated properly. As a result, the car will overheat.
How to Solve This?
- You should inspect the blower fan visually for broken components. If the blower fan is physically damaged, replace it. If the fan has no damage, try connecting jumper cables between the battery and the blower motor.
- If the fan doesn’t run, a blown fuse can be the problem. Open the fuse box and locate the fan fuse. The diagram on the fuse box cover will be helpful in finding the right fuse.
- Pull the fuse out and install a new fuse. The fan should now run properly, and the car overheating problem will be gone.
2. The Thermostat Is Malfunctioning
A thermostat is responsible for the proper flow of coolant through the engine channels and the radiator. If the thermostat valve is stuck at a closed position, fully or partially, the coolant flow through the radiator isn’t enough.
When the AC is on, the heater can draw some of the heat. It reduces the impact of the faulty thermostat. But if the AC is off, the bad thermostat will cause overheating.
How to Solve This?
- Turn the engine off and let it cool down. Then, pop the hood.
- Find the thermostat near the end of the top radiator hose.
- Ask a friend to start the engine. If the thermostat is working properly, the hot coolant should flow through the hose, and you can feel it.
- If the hose doesn’t get warm, there is a problem with the thermostat. You should get the thermostat replaced by an expert mechanic. It will cost about $250-$350, including parts and labor.
3. Leak in the Cooling System
The cooling system in your car consists of various components, including hoses. Over time, these hoses may get brittle and develop cracks. These cracks cause a bunch of problems.
Due to the cracks, the pressure inside the cooling system will drop. As a result, the coolant flow will not be enough to dissipate the heat from the engine. Coolant can also leak from these cracks.
Another common problem is the presence of air bubbles in the cooling system. Due to the air bubbles, the cooling performance of the coolant drops. So, your car will overheat even when the AC is off.
How to Solve This?
- You need to take multiple steps to solve the problem. The first step is to check for any leaks or cracks in the hoses. If so, you must replace the hoses and connect the new hoses tightly.
- After replacing the hoses, you should purge air from the system. To do this, you need to open the radiator cap. Then, pour some fresh coolant into the radiator.
- Loosen the purge valve and turn the engine on. Let it idle for about five to ten minutes. During this period, the air bubble will be removed from the system.
- Then, you need to top off the coolant until the level reaches the FULL mark on the reservoir. Tighten the pressure cap. Once the air bubbles are removed, the cooling system will work better and prevent overheating.
How to Prevent Car Overheating When the AC Is Off?
You should follow the tips below to prevent overheating.
- Don’t let the engine idle for a long time. For example, if you are in heavy traffic, consider turning off the engine. As airflow is lower when the car is idle, it causes overheating.
- Running the air conditioner all the time reduces the service life of AC components. Over time, these components impact the cooling performance, and the car overheats with the AC off.
- Keep an eye on the regular maintenance schedule. Ensure all the components are working properly and the coolant level is adequate.
- If you aren’t confident enough to repair or replace crucial components, always get help from experienced technicians.
FAQs
Check the following answers to some commonly asked questions about car overheating when the AC is off.
Q: Can the AC get turned off due to high engine temperature?
If the engine overheats extremely, it can impact the AC performance. In modern cars, the ECU can turn the AC off to prevent further damage.
Q: Can I drive a car if it overheats when the AC is off?
You should not normally drive an overheating car. If the car overheats when the AC is off, you can try running the heater at full speed. It will draw some heat. But you must check the reason behind the problem.
The combined operation of the engine and the air conditioner balances the engine heat. But sometimes, the engine can’t dissipate heat properly when the AC is off. So, the car overheats when the AC is off. The most common reason behind this problem is a faulty blower fan or a bad thermostat. Coolant system leaks, low coolant levels, and air bubbles can also cause the engine to overheat. If you face this problem, you should take prompt action to solve the problem. Otherwise, crucial engine components can face irreversible damage.