How to Check Your Car at Home to See If Freon Is Needed
- 1). Set your A/C unit to its coldest setting while the vehicle is in motion. Insert the tip of a thermometer into the middlemost vent and hold it in place for at least one minute.
- 2). Pull to the side of the road and check the thermometer's reading. If the range is anywhere from 42 to 55 degrees Fahrenheit, your Freon levels are in no need of recharging. If the displayed temperature is greater than 55 F, proceed to the next step.
- 3). Don your gloves and open the hood of your car. Locate the low-pressure line, which is large, steel and topped by a blue cap. The low-pressure line is located on the passenger side of most vehicles. Avoid the high-pressure line, which is topped by a red cap.
- 4). Unscrew the blue cap on the low-pressure line and connect it to the A/C pressure gauge using the snap-on fitting.
- 5). Start your vehicle and turn your A/C unit to its coldest setting. Allow the needle on the gauge to stabilize.
- 6). Read the gauge. If the needle is within the green panel on the gauge or indicates a reading of 25 to 45 psi (pounds per square inch), your Freon levels are acceptable. If this reading is lower, you will need to add more refrigerant.