AC Off Due To High Engine Temperature: Fixed!

Ah, the sweltering summer days, when the heat and humidity are so high that you feel like you’re living in a sauna. It’s a dreaded time for Chevy Cruze or other cars’ owners, as the increased temperatures can cause a myriad of problems, one of the most common being an AC off due to high engine temperature

When your car’s AC turns off due to high engine temperature, you will be left feeling frustrated and desperate for a solution. Fortunately, there are a few things you can do to get rid of engine hot AC off condition, and get your car back up and running with a nice cold AC. In this article, we will discuss what causes your car’s engine to overheat and how you can fix it so that your AC can be running again as soon as possible.

When your car’s engine temperature gets too hot, you may find that your air conditioning (AC) has automatically shut itself off. This is a normal safety feature of your vehicle as it is designed to first protect your engine from damage when it gets too hot. The first step is to understand why your engine temperature is high. While it may be due to a faulty thermostat, it could also be a sign of a larger problem, such as a clogged radiator. Secondly, you should check the coolant level. If the coolant level is low, the engine will have trouble cooling down. Apart from the engine, other components of the air conditioning system can also contribute to the issue. The condenser, compressor, and other parts may be clogged, blocking the flow of cold air. This can cause the system to overheat and the AC to switch off. 

Also Read: Car AC Not Blowing Cold Air When Idle

First Thing You Should Do If AC Off Due to High Engine Temperature

 If the engine overheats, the AC will automatically shut off to reduce the load on the engine. The first thing you should do is to check the temperature gauge on the dashboard to ensure that the engine temperature is indeed high. If the engine temperature is not that high on the gauge, but still AC is turned off by the engine’s computer, the chances are that there is an issue in the engine’s cooling system.

The cooling system is made up of the radiator, water pump, thermostat, and other engine coolant temperature sensor. The water pump circulates the coolant throughout the engine and radiator to keep the engine from overheating. The thermostat regulates the amount of coolant that is circulated through the system. If there’s any error in the engine temperature control system, your engine may overheat, and your engine’s computer can also throw an OBD2 error code. 

P0128 code is the most common in such cases. You can use this OBD2 tool to find the root cause of engine overheating. After fixing issues, you need to clear codes using the OBD2 scan tool.

Here’s how you can do:

There are also pending trouble codes when the vehicle’s computer detects a problem with the engine but not to the point that a fault actually exists. Luckily, the Bluedriver OBD2 tool, I linked above, also shows those pending trouble codes.

Can You Drive With AC Off and High Engine Temperature?

When the “Engine Hot AC Off” warning light comes on in your car, it’s not a situation you should take lightly. This warning light indicates that your engine temperature is too high and your air conditioning has automatically been shut off to prevent further damage to your car.

While it may be tempting to continue driving, this could cause severe damage to your vehicle, which is why we strongly recommend that you pull over to the side of the road as soon as possible. 

If the temperature gauge in your car is in the red zone, it’s a sign that your car is running extremely hot and needs to be cooled down. Driving with a high engine temperature can cause serious damage to your engine and other parts of your car, such as the radiator, thermostat, and hoses. It can even result in a blown head gasket, which can be a costly repair. 

In such cases, turn off the engine, pop open the hood and let it cool off. Don’t open the coolant reservoir or try to add coolant until the engine has cooled down, as this can cause bodily injury. 

However, I have seen cases the temperature gauge on your dashboard either stops working or the needle of the temperature gauge sticks at ‘C’. This is normally due to the failure of the engine thermostat or coolant temperature sensor.

How Does Car AC Relate To the Engine’s Cooling System?

The AC compressor gets power directly from the engine’s crankshaft via serpentine belt. As the AC compressor runs, it uses a part of the engine’s power and exerts strain on the engine. As a result, the engine has to work hard to generate more power and compensate for the power consumed by the compressor.

If the engine overheats or the engine’s computer (ECU) detects any error in the readings sent by the engine coolant temperature sensor, the ECU will assume that the engine has overheated. As a result, the ECU will disengage the AC compressor, due to which AC will stop blowing cold air. This is done to prevent extra strain on the engine.

Note: Even if the engine’s temperature is optimum and there is no harm in the engine, the ECU makes decisions solely based on the signals sent to it by the sensors. If sensors have any error and the readings go out of the specified range, the ECU will interprete it as a fault in the engine, and perform necessary tasks to prevent the engine from damage.

Causes Of AC Off Due To High Engine Temperature Chevy Cruze

Here are the causes of engine hot AC off condition:

1. Clogged Radiator

When it comes to the cooling system of your car, the radiator plays a huge role in maintaining the engine temperature at a safe level.

The primary role of your radiator is to transfer heat from the engine coolant to the air, thus allowing the heat to dissipate and keeping the engine cool.

But, when a radiator becomes clogged with debris and dirt, it restricts the airflow and the heat transfer process doesn’t take place as efficiently.

As a result, the engine temperature begins to rise, and your car’s computer will sense the high engine temperature and shut off your AC as a preventive measure.

How to spot?

The radiator can be clogged both from the inside and outside. If the radiator is clogged inside, the hose and tubes will be blocked with rust-like sludge that will prevent a smooth coolant flow through tubes and hoses. This usually happens when the coolant loses its anti-corrosion properties and becomes more acidic with age.

If radiator fins are clogged i.e. radiator is clogged from the outside, it will disrupt the airflow. Furthermore, you should also visually inspect if the fins of the radiator are bent or not. If they are bent, it will also affect the airflow over the radiator fins and cause engine overheating.

clogged radiator sign

One way to check if a radiator is clogged is to use an infrared thermometer and check the temperature at multiple locations. If the temperature is not consistent, it could indicate a clog.

If the engine is running for a long time and the lower hose is not warm, it might indicate that the radiator is clogged. 

The best way to clean a clogged radiator is to perform a radiator flush procedure

To flush the cooling system:

  1. Drain the radiator by removing the valve in the bottom of the radiator.
  2. Plug the radiator valve and fill the radiator with distilled water.
  3. Start the engine and drive for around 20 minutes. Make sure that you run the heater on high mode.
  4. Flush the water from the cooling system.
  5. Add the recommended coolant/antifreeze into the engine with a 50/50 ratio.

2. Faulty Radiator Fan

The radiator fan is responsible for blowing air through the radiator which helps in dissipating the heat from the cooling system. When the radiator fan is faulty and stops working, the engine’s coolant temperature rises, leading to a high engine temperature. This, in turn, causes the AC to shut off automatically. 

The radiator fan is normally connected to a relay and it is the relay that controls the fan’s power supply. If the relay fails, the radiator fan will not operate.

How to spot?

To diagnose a faulty radiator fan, you should first check the fuse to make sure it’s in good condition. If the fuse is blown, you’ll need to replace it. You should also check the relay of the radiator fan. Lastly, you should test the harness connector of the radiator fan.

I found the below youtube video really helpful to test the relay and harness connector of the radiator fan:

3. Leaking Coolant or Low Coolant Levels

Coolant, or antifreeze, is essential for keeping the engine running within its optimal temperature range. It’s made up of a mix of water and chemicals that help to regulate the temperature and prevent the engine from overheating.

When the coolant levels are low, the engine won’t be able to cool itself down properly. This causes the engine to start running hotter and hotter, eventually leading to it overheating.

As the engine temperature rises, the AC will be forced to shut off. This is because the AC needs a certain amount of power in order to cool the air. If the engine gets too hot, the AC will be unable to keep up and will shut off as a safety measure. 

How to spot?

First, you need to check the coolant level in the overflow tank. When the engine is cool, the coolant should be between full (Max) and low (Min) marks on the overflow tank.

coolant level check

To detect coolant leaks, you can add this UV dye in the coolant system. When you use a black light, the coolant leaks show right up nice and bright 

The main spots of coolant leaks are:

  • Thermostat
  • Engine coolant temperature sensor
  • Water pump

4. Faulty or Stuck Thermostat


The thermostat is a small valve located at the entrance of the engine’s cooling system. Its job is to regulate the flow of coolant, ensuring that the engine runs at an optimal temperature. The thermostat does this by opening and closing in response to the temperature of the engine.

When the engine is cold, the thermostat remains closed to keep the coolant from entering the radiator. When the thermostat is closed, the coolant keeps on circulating through the passages in the engine without passing through the radiator.

As the engine warms up, the thermostat opens and allows the coolant to circulate through the engine’s passages after passing through the radiator so that engine’s temperature stays at an optimum level.

To locate the thermostat, you just need to follow the upper hose of the radiator as its one end is connected to the thermostat. A thermostat is located closer to the water pump.

How to spot?

If the thermostat is stuck closed, the coolant could not enter the radiator. As a result, the heat from the hot coolant coming from the engine could not be dissipated. This will cause the engine to become overheated. As a result, the ECU will turn off the AC to prevent further damage.

A simple way to test a stuck closed thermostat is to touch the hose that runs from the radiator to the thermostat to see if you can feel water running through it. If you can’t feel it, it means the thermostat needs to be replaced.

5. Faulty Engine Coolant Temperature Sensor

engine coolant temperature sensor

Engine coolant temperature sensor is one of the most common causes of engine hot AC off condition.

The ECTS measures the temperature of the engine coolant. When the temperature of the coolant goes beyond the normal range, the ECTS will send a signal to the car’s computer and the AC will be shut off automatically. This is done to protect the engine from overheating and from the potential damage that can be caused by it. 

When the engine coolant temperature sensor fails, it can’t accurately measure the engine temperature and report it to the car’s computer. As a result, the computer reads the temperature as higher than it actually is. This causes the computer to send a signal to the AC to turn off as a safety measure to prevent your vehicle from overheating. 

Some engines also include two ECT sensors. One is located closer to the thermostat in the cylinder head, and the other is located at the bottom of the radiator. The first one controls the engine’s functions by sending signals to the ECU. The second one is for the instrument panel coolant temperature gauge.

You can follow your vehicle’s manual to find the exact location of the ECT sensor. 

How to spot?

You should check the primary ECT sensor. To test the ECT sensor:

  1. Immerse the tip of the sensor in the water.
  2. Connect a digital ohmmeter to the two terminals of the sensor.
  3. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the engine coolant sensor temperature vs. resistance
  4. Repeat the resistance at other temperatures by heating or cooling the water.
  5. If the sensor does not meet the specification shown in the temperature versus resistance chart, it must be replaced.

You can watch this video to learn more:

If you don’t want to remove the ECT sensor, you follow the following method to test it:

  1. Turn the ignition on.
  2. Keep the sensor connected to the wire harness of the PCM.
  3. Connect the voltmeter across the terminals of the coolant temperature sensor.
  4. When the engine is cold, the voltmeter will read the voltage at around 3 volts.
  5. As the engine warms up, the resistance across terminals of the ECT sensor, the resistance drops. So, the voltage will also drop.

6. Blown Head Gasket

A head gasket is a vital part of any internal combustion engine. It’s a steel, rubber, or aluminum seal that seals the cylinder head to the engine block. It’s also an important factor in preventing coolant and oil mixing.

A blown head gasket is a serious issue that can cause a multitude of problems in your car’s engine, including triggering the AC off due to a high engine temperature warning. A blown head gasket occurs when there is a leak in the gasket that seals the engine block and cylinder head, causing coolant to leak out and mix with the engine oil or combustion gases. 

When a head gasket is blown, it can cause a loss of coolant from the engine. As the coolant level drops, the engine begins to overheat, which triggers the AC off due to a high engine temperature warning. 

How to spot?

Diagnosing a blown head gasket can be tricky, as the symptoms can vary depending on the severity of the issue. Here are some signs that may indicate a blown head gasket:

  1. Engine overheating: If your car’s engine is overheating and triggering the AC off due to high engine temperature warning, it could be a sign of a blown head gasket.
  2. White smoke from the exhaust: If you see white smoke coming from the exhaust, it could be a sign of coolant leaking into the combustion chamber due to a blown head gasket.
  3. Milky oil: If you notice that your engine oil has a milky or frothy appearance, it could be a sign of coolant mixing with the oil due to a blown head gasket.

Engine Hot AC Off: FAQs

How do I know if my AC is shutting off due to high engine temperature?

If your AC is shutting off due to high engine temperature, you may notice your vehicle’s engine temperature gauge rising or the warning light turning on. You may also notice the AC blowing warm air 

How can I prevent my AC from shutting off due to high engine temperature?

To prevent your AC from shutting off due to high engine temperature, make sure your vehicle’s cooling system is in good condition. Regularly inspect the radiator, hoses, fans, and thermostat. Have your coolant checked and topped up if needed.

What Should I Do if My Car Overheats?

If your car is overheating, you should first pull over and turn off the engine. Allow the engine to cool down before checking the coolant level and examining the radiator and cooling system for any clogs or leaks. If necessary, you may need to call a tow truck to take your car to a mechanic for further inspection.

How Can I Lower the Engine Temperature on My Car?

To lower the engine temperature, check the coolant level, check for any broken hoses or leaks, and check for any clogs in the radiator or cooling system. You should also check the fan and make sure it is functioning properly. If all of these components are working correctly, you may need to flush the cooling system and replace the coolant.

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