Does Running the AC Use Coolant? (Answered)

Each and every automotive weather its a car, SUV or truck has a complete air conditioning unit integrated with other systems. This AC system can deliver cold air in summer and hot air in winter as per the user requirements.

Car AC working principal is exatly the same as of your domestic AC system. Car AC system is a close system that circulate a refrigerant to add or remove heat from your car cabin.

For cooling cycle, this refrigerant when pass through the radiator section loose heat and get very cold. This low temperature refrigerant when pass throught evaporator transfer its coldness to the air going into the car cabin. This deliver cold air to driver and passenger sitting in car cabin.

There are people that mix the concept of refrigerant and engine coolant as both work to reduce car temperature. In this article we will discuss, does running the AC use coolant?. We will also discuss how coolant will effect car AC, how to know coolant is working properly, how coolant is different from anitfreezer, and how does it effect humidity.

Does Coolant Have Any Effect on Car AC?

No, car coolant does not have any effect on car AC working or performance. Car AC has its own condenser next to the car radiator to remove heat from its refrigerant.

Car AC system neither use engine coolant nor does it rely on radiator to remove heat from it refrigerant. Both are completely separate system but some user do complain or observe a drop in coolant level or vehicle performance when use AC in a hot summer day.

This is due to the fact that AC system rely on engine for power. Car engine is use to power compressor of the AC system. In a hot summer day when engine cooling system already working at max to keep engine cool.

Extra load of AC on engine will make engine even more hotter and force cooling system to increase coolant flow. This may effect coolant level indication or engine performance.

What are the Differences between Antifreeze and Coolant?

The main different between car antifreezer and coolant is the amount of water you put in the ethylene glycol or propylene glycol. If you use glycol with a small amount of water then its a antifreezer and its 50 percent water and 50 percent glycol then its coolant.

Ethylene glycol or propylene glycol are two main fluids being used for antifreezer or coolant. Main purpose of the glycole is to protect water from boiling when engine is running and temperature is too high thus called coolant. Glycole also protect water from freezing when engine is not running and outside temperature is freezing cold thus called anitfreezer.

How to Know if Your Coolant Is Working Correctly?

The main purpose of car coolant is to keep your car engine cool during driving or ideling. If your engine is performing well and you are not facing any engine heat related problem then you can know that your coolant is working correctly.

In all cars there is a separate storage, pump, filter, channles, and radiator for engine coolant to flow. Pump force the coolant to from storage throught the filter and into the channles that passes over then engine. When coolant passes over the engine it abosrb engine height and when its passes thought radiator it transfer that heat to flowing air.

This is how coolant keep engine cool. If engine get heat up you will see check engine light, engine high temperature on car information cluster, and high engine temperature warning light too. These are the sign that your coolant system in not working properly.

How does Coolant Affect the Humidity of the Car?

Car coolant does not affect the humidity of the car. Its the car AC system that controls the humidity inside the car cabin.

Car engine cooling system is completely close and entirly separate from the car AC system. Car engine cooling system pump coolant throught its own separate channels that run over the engine. AC system has its own refrigerant, compressor, condenser and evaporator.

How does Coolant Affect the Airflow of the Car?

Car coolant does not affect the airflow of the car. Air moving into the car cabin throught its AC system is neither controled or influenced by the car coolant. Its the car AC system the control and influence the airflow moving into the car cabin.

How does Coolant Affect the Temperature of the Car?

Yes, it do affect the temperature of the car engine. Car engine coolant is designed to control the temperature of the engine and its related components. If the quantity or quality of the coolant is low then its will affec the temperature and engine performance will be reduced.

How to Know the Car AC Is Low on Coolant?

There is connection between car AC and car engine coolant. Car AC system rely on its own refrigerant system to operate while the car engine cooling system rely on engine coolant to keep the engine temperature under control.

How to Know the Car AC Is Low on Coolant

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AC Gauge Reading and How to Check the Level of AC Coolant in the Car?

You can mount a manifold gauge on the high-to-low-service port if you want to measure the pressure of your car’s AC system. It is an easy method to do.

Connect the high-side gauge hose, which is red, to the high-side service port, and the low-side gauge hose, which is blue, to the -side service port. 

Now turn off both engine and AC and release the gauge knobs. In this case, the constant pressure on the gauge will be 80 to 105 psi. 

Leaving the car idle and setting the AC to the highest level, the low-side gauge reads 25 to 35 psi and the high-side gauge 200 to 350 psi. When these results are low or even zero, it means that there problem with the system likely car is running out of refrigernat.

Hot Air Is Coming Out of the AC

Hot air is coming out of your car AC due to the low level of refrigerant in the AC system.

The efficient working of the entire car AC system rely on the refrigerant quality and quantity. Any change in refrigerant quantity and quality will affect the AC performance.

Failed to Engage AC Clutch

Turn on the car’s AC and keep listening to it. Heard a ‘click’ sound? If yes, then know that it was the sound of clutch engagement and it means that everything on the AC is working properly. 

The significance of this clutch engagement is that it reads the refrigerant (Freon’s) level and works by allowing the compressor to compress Freon. 

However, this clutch will fail to engage when the AC’s freon level drops too low. This indicates insufficient refrigerant to compress the compressor.

Disruption of Cooling Capacity

When the car’s AC system loses its freon, its cooling capacity decreases. If the Freon drops slightly below the correct level, you will notice a difference in the cooling power of the AC.

You will see that the AC is releasing relatively less cold air. Also, if there is a leak in the cooling system of the AC, there is a deficit in its performance.


If you ask if the coolant affects the AC, the direct answer is No. The coolant doe not affects the temperature of your car’s AC. It the AC system refrigerant that make the AC system work.

Whenever the refrigerant level in your car drops too much, the inside temperature will change according to the outside of the car. Such as burning temperature on hot days and freezing temperature on cold days.

If the car’s AC system is damaged or defective due to lack of refrigerant, it can cost a lot to repair or replace it. So if you have such a problem in your car then take quick action without delay.

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.