How To Check Freon Level In Car and Recharge It | DIY Guide
Even though cars should never lose freon in ideal conditions, on average, cars lose between 3% and 8% of freon each year. If you suspect that the freon level in your vehicle is at a minimum, you’ve come to the right place. In this article, I’ll show you how you can check your car’s freon level and recharge it if needed.
Since I like doing car care and car fixes by myself, I learned the proper way of checking freon levels, and the best thing is that you won’t need a lot of tools to do it. If you’re a DIYer like me, you may already have the equipment to check it.
Symptoms That The AC Refrigerant Level Is Low
Before we dive into the exact steps, I will briefly discuss some common symptoms of low freon levels in your vehicle.
AC is Blowing Warm Air
There’s nothing worse than your car blowing warm air while trying to cool down the vehicle during sunny days. It happened to me on a road trip, but luckily, I immediately found a car shop that refilled the freon.
Warm air is the most common symptom of low freon in your vehicle, and that usually means that the freon level is extremely low since it can’t blow the cool air at all.
Loud AC Compressor
AC compressors tend to get loud when there’s not enough freon. Without a freon, the compressor has to work much harder, and that’s why they become very loud, especially when you’re just turning on the AC.
AC compressors are extremely expensive to replace, and by driving with low freon levels all the time, you could break the compressor.
Ice Around The AC Compressor
When ice forms around the AC compressor, that’s a big sign of a low freon level in the system. That happens because evaporator coils cannot absorb enough heat from the cabin air.
Sometimes, the ice won’t form around the compressor if it’s not too hot outside, and you didn’t pick the lowest settings on your AC. That’s why I always tell people not to judge based on one symptom only.
Sweet Smell In The Cabin
This doesn’t happen very often, but if you notice a sweet smell in the cabin coming from the vents, it may be a sign of a freon leakage, especially if the sweet smell is combined with warm air and loud noise from the AC compressor.
The Car Used To Blow Much Colder Air
This may be subjective, but if you think that your car used to blow much cooler air, and now you don’t think it’s the same, it may be a sign that there’s not enough freon in the system.
When this happens, the compressor still has some freon, but soon, all the freon will leak, and the car will start blowing warm air through the vents.
Types of Car Refrigerants
There are three main types of refrigerants used in vehicles. They all have different names, so I didn’t want to confuse you straight away. I call them freon all the time in this article. However, since there are differences in these refrigerants, I need to explain this to you before we continue with the article.
3 types of car refrigerants (freons):
- R-12
- R-134a
- R-1234YF (HFO-1234YF)
R-12 has been in the past, and because it was extremely pollutant to the environment, around 1994, most vehicle manufacturers stopped using it. Since there’s almost zero chance that you have this type of refrigerant in your vehicle, I won’t mention it anymore, but it’s good to know about it.
R-134a is the most common type of car refrigerant. It has been used in all cars from 1994 up to today. However, since the world became even more conscious about the environment, they developed even safer car AC refrigerants (but more expensive).
R-1234YF or HFO-1234YF is the newest type of car AC refrigerant. It’s the most environmentally friendly car AC refrigerant (Freon) many car manufacturers use today. Not all cars implement this gas since it’s pretty expensive, but there’s a chance that it’s in your vehicle if the car is from 2012 and beyond.
I had to briefly show you these types since each type of freon has different pressure measurements.
How To Quickly Check Freon Level In The AC System
I used this method while driving a Peugeot 308, which always had air conditioner refrigerant leakage problems. Before every regular maintenance check, I would check the freon level in the vehicle, and if everything were fine, I would drive the car without the fear of a sudden cooling system failure.
You don’t need a lot of equipment, just a manifold gauge set, safety glasses, and a thermometer. I highly recommend these Orion Motor Tech AC Gauges. And for the thermometer, you can use a simple home thermometer that can read as low as 30°F.
If you know someone who works as an air conditioner technician, you can borrow the equipment; they all have professional AC gauges. That way, you can save some money. Now that you have gathered the equipment, let’s see the steps.
Step 1: Locate the high side and low side pressure on your car’s AC system
Open the hood and locate the two AC lines in the engine bay. They should be somewhere near the AC compressor. On most cars, it’s somewhere on the left when you open the engine bay.
The low-pressure line is thicker but has a smaller valve. The high-pressure line is thinner but has a larger valve. On most cars, the caps on service ports will have an “L” for low-pressure and “H” for a high-pressure service port.
When you locate those, you can remove the caps. Just make sure to put them somewhere safe so you don’t lose them.
Step 2: Connect the manifold (HVAC) gauges to service port valves
Now you should take your manifold gauges and connect them to service port valves on the AC system. Connect the blue hose to the blue side of the gauge and the red hose to the red side of the gauge. Make sure the valves on the gauge are closed (and don’t open them during the whole process).
Connect the other end of the blue hose to the low-pressure (low side) service port. You’ll hear a pop when it fits properly. Try to wiggle it a little bit just to check if everything’s tight. When it’s tight, you can now open the valve connected to the service port by turning it to the left.
Now let’s connect the second (red) hose, which should be connected to the high-pressure (high side) service port on the car’s AC system. Again, make sure everything fits properly and that it’s tight, and then you can open the valve connected to that service port.
Step 3: Start the vehicle and turn the AC on to the lowest possible temperature setting
To make the readings as precise as possible, the car and the AC should be turned on. Also, the lowest temperature settings on the AC must be chosen. The fans can stay on low speed, even though I always keep them somewhere in the middle.
Now you should also mount the thermometer to the vents so that it can measure the temperature of the air from the AC.
What I also like to do is to open the windows, so that the AC never cools the car completely. That way, the compressor won’t stop working in the middle of the check.
Let the car run like that for 3-5 minutes, and then we can continue to step 4.
Step 4: Check the readings on the gauge
Now it’s time to check the readings on both blue (low-pressure) and red (high-pressure) gauges. Since the readings depend on the outside temperature, I made quick charts you should follow for proper readings.
I made separate charts for R-134a and R-1234YF freons, so you can easily follow them. By the way, if you still don’t know what type of freon you have in your car, every vehicle should have a sticker somewhere around the engine showing the freon type – so make sure to check it out.
R-134a Temperature Pressure Chart
| Outside Temperature | Low-Pressure Gauge | High-Pressure Gauge | |
| 65°F | 18°C | 25-35 psi | 135-155 psi |
| 70°F | 21°C | 35-40 psi | 145-160 psi |
| 75°F | 24°C | 35-45 psi | 150-170 psi |
| 80°F | 27°C | 40-50 psi | 175-210 psi |
| 85°F | 29°C | 45-55 psi | 225-250 psi |
| 90°F | 32°C | 45-55 psi | 250-270 psi |
| 95°F | 35°C | 50-55 psi | 275-300 psi |
| 100°F | 38°C | 50-55 psi | 315-325 psi |
| 105°F | 41°C | 50-55 psi | 330-335 psi |
| 110°F | 43°C | 50-55 psi | 340-345 psi |
R-1234YF Temperature Pressure Chart
| Outside Temperature | Low-Pressure Gauge | High-Pressure Gauge | |
| 65°F | 18°C | 22-32 psi | 128-142 psi |
| 70°F | 21°C | 27-38 psi | 140-155 psi |
| 75°F | 24°C | 33-43 psi | 148-166 psi |
| 80°F | 27°C | 40-45 psi | 175-210 psi |
| 85°F | 29°C | 46-56 psi | 227-253 psi |
| 90°F | 32°C | 46-56 psi | 255-275 psi |
| 95°F | 35°C | 53-57 psi | 280-310 psi |
| 100°F | 38°C | 53-57 psi | 325-310 psi |
| 105°F | 41°C | 53-57 psi | 350-360 psi |
| 110°F | 43°C | 53-57 psi | 350-360 psi |
When you read both gauges, if the PSI on both of them is in the range as shown in the table, the freon level in your car is probably fine.
If both gauges show lower values, you’ll probably have to recharge the refrigerant in the AC system.
However, suppose you read any of the following. In that case, I highly advise you to visit a professional mechanic:
- Low-side pressure and high-side pressure gauge show similar readings
- The low-side pressure gauge is low, but the high-side pressure gauge is high
- The low-side pressure gauge is high, and the high-side pressure gauge is low
- Both gauges show higher readings than normal (probably a refrigerant overload)
Lastly, don’t forget to check the thermometer inside the vehicle that you mounted on the vents. If the AC is working correctly, the cool air coming out of the vents should be around 40°F-45°F. If it’s higher, that’s another sign that you should recharge the freon.
When you’re finished with everything, don’t forget to close the valves on the hoses, unplug them, screw the caps back to the high and low side pressure service ports, and store the equipment, so you have everything ready for the next time.
How To Recharge Freon At Home
If you followed all the guidelines above and from the gauge readings, you could suspect that there’s a lack of freon in your car’s AC system. Here’s a simple DIY guide to recharge car refrigerant at home with basic equipment only.
What you’ll need:
- Car AC refrigerant recharge kit
- Safety glasses
- Safety gloves
Before ordering parts online, make sure to find the sticker with AC information. It’s located somewhere in the engine bay. Over there, you should find info on what type of refrigerant your car has and how much of it should be in the system. You can always check the car’s manual if you don’t see the sticker. You can order the right freon type when you find the info.
For R-134a, I recommend you buy this AC Refrigerant Recharge Kit on Amazon. It’s a great all-in-one kit in which you get the gas, the hose, and the gauge to measure the pressure in the system.
For R-1234yf types of refrigerant, I suggest you buy this ZeroR® Permafrost Refrigerant Recharge Kit. They provide you with a can of R-1234yf gas, a hose, and a gauge to measure the low side pressure of the AC system.
Since these two products have slightly different steps to fill the AC system with freon, I’ll explain each separately. Actually, the steps are the same, but the products are a bit different.
Before doing any of the steps below, wear safety gear. Chances of something bad happening are minimal, but it’s better to ensure your safety.
Recharging R-134a Freon With Recharge Kit
Here are the quick steps you should take:
- Find a low-pressure service port in the engine bay and remove the safety cap.
- Turn on the vehicle and get the AC going (fans to high, AC to maximum cool, and turn on the recirculation option)
- Attach the hose to the low-side pressure service port and check the readings. If the gauge goes to the red area, I suggest you visit a mechanic. If it shows green, your freon level is fine. If the readings show that you’re low on freon, disconnect the hose from the service port and continue with step 4.
- Shake the can well, connect it to the gauge, and reconnect the other side of the hose to the low-side pressure valve.
- Slowly shake the can up and down and left and right, and pull the trigger (keep it pulled) for around 10-15 seconds. After that, release the trigger, and check the pressure readings.
- Repeat step 5 until the pressure readings show that the freon is filled (the gauge should stay in the middle of the green zone). When the gauge is in the green zone, proceed to step 7.
- Disconnect the quick-connect coupler from the low side port, and screw back the original cap.
- The AC system should now be completely recharged with freon, and it should start blowing cold air from the vents.
Recharging R-1234yf Freon With Recharge Kit
Quick steps you should take:
- Turn your vehicle on, set the AC to max cooling, fan speed to max, and turn on the recirculation.
- Attach the hose with a valve end to the can and the other end to the low-side service port on your car. Make sure that the valve on the can is closed.
- Check the readings on the gauge first. If the gauge is in the green zone, you’re low on freon. If the gauge is in the blue zone, the freon level in your car is fine. And if the gauge is in the yellow or red zone, there’s too much freon in the AC system.
- If the readings show that the car is low on freon, you can now flip the can upside down and open the valve to release the refrigerant into the AC system.
- After 10-15 seconds, close the valve and check the readings again.
- Repeat step 5 until the pressure gauge shows the AC system is full of freon. Make sure not to overfill the system.
- When you’re finished, disconnect the hose from the low-end service port and screw back the original cap. Furthermore, disconnect the hose from the gas can as well and store it properly.
- Now that everything’s finished, your car should have an ideal amount of freon in the AC system, and the cooling should be like new again.
Final Check With a Thermometer
After you have successfully recharged the gas in the AC system of your vehicle, I recommend you do a final check by using a thermometer. Any thermometer with a probe should be fine.
Just mount the thermometer on the air vents in your vehicle, turn the AC on (max fan, max cooling), and wait a few minutes to read the results.
The ideal temperature the AC should blow should be in the 35-45°F range.
If the temperature is more than 50°F there are three possible causes:
- You didn’t fill the freon enough
- The outside (atmosphere) temperature is extremely hot (+110°F), and it’s very humid
- There’s some other problem with your AC system
If you suspect some additional problems with your AC system, I highly advise you to visit a mechanic.
Last Words
As you can see, checking the freon level in your car’s AC system and recharging it isn’t rocket science. If you’re a DIYer, I’m sure you’ll be able to do all the steps correctly. By self-recharging the freon, you can save a lot of money.
On average, recharging freon in the shops may cost you anywhere between $150 and $300. And if you do it yourself, you can recharge the freon for $50-$80.
I hope that you’ll find this guide on checking freon levels and recharging it useful. If you’re not completely sure that you understood everything, I also suggest you check the video by ChrisFix, where he explains the steps to recharge the R-134a in his BMW. That way, you’ll get an even better picture of what you should do.