If you had to choose one accessory on your vehicle that you simply couldn’t live without, what would it be? The radio? Heated seats? Air conditioning?

On a 95-degree day, no matter where it fell on your list before, chances are the AC moved quickly to the top. 

You’re stuck in traffic. You have a meeting to get to. The temperature keeps climbing up, up, up!

You turn up the AC unit one more notch. The cool air feels great. 

And then suddenly, everything changes. You feel it in your car’s behavior. The cool air isn’t so cool. The temperature gauge starts to climb. You hear noises that weren’t there before. You play around with buttons and dials, trying to find the cause. 

You’ve determined the car overheats when the AC is on. 

Why is your car overheating when the AC is on?

There are several reasons why a car might overheat when the AC is on and running full blast trying to keep you cool. The likely causes include:

It could be an AC compressor overload. When you turn the AC on, the compressor starts to work with the engine to move and compress the refrigerant cylinders, which builds pressure inside the engine. A car’s air conditioner draws significant power from the engine. If you’re putting a high load on the compressor and it isn’t in top shape to perform the task, eventually, it will make the car overheat. A high load will damage the AC compressor over time, preventing it from blowing cold air out into the passenger compartment. If this continues to fester, the car engine can overheat, causing more problems within the engine compartment over time.  

It could be a malfunctioning cooling system. It’s one of the most common reasons for an overheating car. Problems often start small, such as a leak in the radiator. It’s running out of water and needs refilling to keep it operational. It might be a buildup of dirt or debris in the radiator, preventing fluids from moving smoothly throughout the system. Take a look at the radiator; do you notice corrosion or other buildup on the surface? While the radiator can be washed off with a low stream of water, it might also be a sign of a bigger problem. Bringing it in for a full inspection will help pinpoint the situation to determine what repairs will get it back to working condition. 

It could be a problem with the fan. A lot of city driving is based on sitting in traffic, waiting at stop lights, and idling. If the air isn’t flowing correctly into the radiator, it can overheat. It can be caused by several things, including a blockage in the fins, a faulty electric fan, fan clutch, or fan switch. If you notice the car overheating more during idle situations, the engine fan probably is clogged or dirty, with lowered levels of airflow throughout the system. 

It could be the radiator. The radiator is designed to pass coolant into the engine. That’s why the radiator plays an important role in your car’s overall functionality. If the radiator works correctly, it passes coolant over metallic fins into the engine, which helps the vehicle operate properly. If this process has any faults in the system, the coolant is disrupted, which leads to problems within the cooling system. Suppose you start to see the engine temperature climbing after you turn on the AC. In that case, it’s a good idea to check the radiator and ensure the various components operate as designed. 

It could be a problem with the coolant temperature sensor. Today’s modern cars are built with multiple sensors to help alert you to potential problems before they impact the functionality of the vehicle. While it’s rare that a coolant temperature sensor would go out and allow the car to overheat, if you’ve considered other possibilities and still can’t find the problem, this is worth checking out. The coolant temperature is measured by the sensor and compared to the temperature within the dashboard system. If there is a discrepancy in the readings, it could cause the dashboard light to illuminate, signaling a problem. If it reads normal, but the temperature still continues to climb, it could also be a malfunction in the thermostat. To fix the thermostat or the coolant temperature sensor, bring your vehicle to a professional mechanic for replacement. 

It could be a fault in other components. Every time you drive your vehicle, it can be impacted by many different things:

• The environment
• The weather
• Potholes
• Bumps
• Extreme heat
• Extreme cold
• Sudden stops
• Urban driving conditions 

The list is never-ending. Parts wear out, sometimes in a manner you might not expect. You can be diligent with your routine maintenance, carefully watch manufacturer’s suggestions to replace parts at peak times, and still experience sudden problems with different components in your car. 

If the compressor, condenser, evaporator, or refrigerant aren’t in proper working condition, they will impact the way your AC unit functions. And when the temperatures start to climb, it leads to the engine overheating. 

What to do if the car overheats

Sometimes you can do everything right and the engine still overheats. The first thing you should do is turn the AC system off, and pull over to a safe spot off of the road. 

Do not try to open the hood of the car, especially if you see smoke coming from around. Steam is scorching, and can severely damage your hands, eyes, and face. 

If it’s a one-time problem, solutions can include:

• Cleaning the radiator – it’s one of the most common reasons for overheating, especially if it’s clogged and antifreeze and water can’t pass through to the engine. 
• Checking the compressor – if you hear any noise coming from the compressor, bringing it in for inspection will ensure it’s operating properly. 
• Flushing the cooling system – if coolant is low or is compromised, it isn’t working as it should. A coolant flush will ensure proper antifreeze levels are topped off inside the system. 
• Check the refrigerant – this is an essential ingredient to help keep your AC unit functional. If refrigerant levels haven’t been checked in a while, a visit to a professional mechanic will ensure its functioning. 

Final words

With over 10,000 parts, every component works together to perform well under all the driving conditions you incur each day. When you notice a change in the way your vehicle drives, it’s a sign it’s time for an inspection. 

Finding the solution early can fix the problem before it escalates into something bigger and more expensive. If you notice an issue with your AC unit, bring it in today so we can check it out. 

We’ll have you back on the road in no time.