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What’s the Difference between Temperature and Pressure?

If you own a car over 8 years old, you may have noticed that your A/C vents aren’t blowing as cold as they used to. As cars age, so do their parts. While much of your air conditioning system is made of metal, including the high pressure lines, rubber is still a key component. Rubber O-rings, gaskets, grommets, hoses and other parts tend to degrade over time with exposure to heat, humidity and seasonal environmental changes. As that happens, the rubber parts start to harden, crack and fail. Those failures can cause loss of refrigerant in your A/C System. On average, cars over 7.5 years old start losing refrigerant and thus cooling capacity for the air conditioning unit. The solution may be as simple as a 15-minute DIY at home. In this article, we will explain the difference between temperature gauges and pressure gauges that most DIY products have and why the Patented AccuFill® Recharge Tool is more effective than all other products in the market.

First, it is important to understand the air conditioning system, how it works and the changes in technology that have prompted changes to A/C recharge tools. Air conditioners use refrigerant to cool cabin air in your vehicle. This works by compressing this refrigerant from low pressure to high pressure. Compressed gas flowing from high pressure to low pressure rapidly cools. If you have ever used a can of keyboard duster, you will notice that while spraying the gas from the can (high pressure) to your keyboard (low pressure), the can gets cold. The same premise is used to cool your car. Car A/C compressors compress refrigerant from low pressure to high pressure and back, causing a cooling effect on the refrigerant coils. The blower or fan then blows your recycled cabin-air over these cold coils, dropping the air temperature and redistributing it through a car’s vents.

Traditional Single Pressure Gauge

Traditional DIY kits utilize pressure gauges, measuring the pressure of the “low pressure port” of your vehicle to determine when the correct amount of refrigerant is added. This method worked on older cars because the orifice between the low pressure and high pressure was a fixed diameter. When the compressor would stop, the low and high pressure sides would equalize, so that a measurement of the pressure in the system was accurate. However, over the years, car A/C technology advances added a Thermal Expansion Valve (TXV) to replace the fixed orifice between the low and high pressure sides. This TXV is a dynamic orifice that releases refrigerant from low to high pressure as needed for more efficient operation and cooling. The challenge is that using traditional pressure gauge recharge tools in these newer systems often leads to overcharging your vehicle. Since the TXV only releases refrigerant as needed, the high and low side pressure never equalizes, so it’s not possible to get an accurate measurement of the pressure in your system. This causes inaccurate fill rates leading to too much refrigerant in the system. This can cause long-term damage to your compressor and seals.

Patented AccuFill® Vent Temperature

All A/C systems work the same in that the air is blown over cold coils causing a finite energy transfer in the form of cooler air. Using that logic, why would you care about the level of the pressure in your system? If the air that’s being released is cold, that’s all that matters. And that’s the focus we used to develop Mister Freeze Recharge Kit with Patented AccuFill® Recharge Tool. Mister Freeze utilizes the Patented AccuFill® Recharge Tool that measures the temperature blowing out of your A/C vents, NOT the pressure in your system.  By this direct temperature measurement, you simply charge your car’s refrigerant until the air coming out of your vent is cold. This method directly measures the cooling performance of your car’s A/C system as you recharge and prevents overcharging –not an arbitrary pressure target that allows inaccurate pressure readings that traditional pressure gauges measure.  Additionally, Mister Freeze’s AccuFill® Trigger uses a wireless digital temperature sensor so you can read your vent temperature while you are recharging your vehicle. You never have to leave your fill position to check air temperature. 

The Importance of Refrigerant

Why is refrigerant important? Refrigerant is used in your car to help cool the cabin temperature. The most common type of refrigerant used today in your car is R134a, as it has low flammability and is safer compared to other refrigerants. It’s gentle on the environment. Your vehicle’s A/C system cycles this refrigerant from low pressure (gas) to high pressure (liquid) and back. It’s this change in form of refrigerant from high pressure to low pressure that has the cooling effect for your car’s cabin air. When you have too little refrigerant, there is not enough pressure differential between the high and low pressure to create that cooling effect as there is not enough pressure in the system. Alternatively, when there is too much refrigerant, there also isn’t enough pressure differential to create that cooling effect as there is too much pressure in the system. It is important to have the right amount of refrigerant in your system to operate efficiently to cool your vehicle.

Mister Freeze is the Solution

AC Technologies Corporation specializes in cutting-edge DIY solutions for your car A/C refrigerant needs and strives to provide viable DIY solutions to save time and money, compared to similar products and services. Our Mister Freeze Brand of Refrigerant along with our Patented AccuFill® Recharging Tool that uses a digital temperature reader is a universal solution to all vehicles in need of refrigerant. To learn more, go to