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How To Recharge Your Car AC With R-134A

The two High and Low AC lines all cars have

The two High and Low AC lines all cars have

Easy Do It Yourself

When your AC in your car is not cooling as it should and is blowing warm or cool air even when on a cold setting, odds are you need to recharge (add) more fluid to the system.

In older cars, car manuals may tell you to add a Freon or similar fluid, this could be an issue since it is hard to get, but in most cases, the fluid needing to be added is called R-134A. Refer to your auto manual. You can buy this at most auto car stores or even in Walmart starting at around $20+. Don't be fooled by a higher price in some, R-134A is the same regardless of how it is packaged, so what you pay is for the extra packaging or features.


1. Start your engine and let it run for five minutes to warm up. If the car is already warm or hot, go to Step 2.

2. Turn on your AC temp and fan to high output.

3. Locate the High AC line. In the photo, this will look similar to the larger diameter pipe. Some cars will have a access cap with H, indicating it is the High line. The smaller diameter pipe in the photo is the L (Low line) of the AC system. The cap on this has a L label. The photo is from a 2013 Honda Civic. The High line is to the right of the windshield fluid container with blue cap. The Low line is to the left.

4. Always read the instruction on the can of R-134A purchased. Most will indicate that you should check the pressure of the HIGH AC line. Some gauges will be color coded, while others are in PSI. In general, if the reading is in blue or between 0-25 PSI, you need to add (maybe something you already know!). If the reading is in the green (25-50 PSI), the AC may not need any more R-134A. If the reading is 25-30PSI, you could add some. If the reading is in the red (55 PSI+), do not recharge the system, as something else is wrong with AC system.

5. Per instructions on the can, attach the hose from the R-134A can to the HIGH AC line. As the AC unit cycles on, read the gauge. If your AC is not blowing cold air when on the coldest setting, you probably need to add some. The point of this reading helps you determine the condition of the AC unit and gives you an idea how much to add. Cars take varying amounts of AC fluid, some may need a full 18 oz. can or more, depending how depleted the cooling fluid is.

6.When you are ready to add, most cans will tell you to turn the valve at the top of the can to open. Make sure the connection is secure from the can to the High Line. Press the trigger on the can and turn the can from the upright position to the 3 o'clock (90 degrees) horizontal to ensure the flow is even, adjust as necessary. As you add, the can will become cold, so wear gloves.

7. Monitor the gauge on the line from the can. DO NOT OVERFILL, as it could damage seals or gaskets. As you add coolant, the AC unit should start to blow much colder air in the cabin. As you add, the gauge will reflect the level (much like a fuel gauge) with the needle rising higher and higher as the AC clutch activates. Stop adding fluid if the gauge approaches 40-50 PSI or when the can is empty.

You are done. The whole process takes 5 minutes. The can may be emptied before the AC is totally filled. The goal is to make sure the gauge that starts in the blue range and ends in the green zone 30-45 PSI. It is better to underfill than to overfill!

If after the coolant does not make your AC blow cold air, there is something wrong with the compressor or there is a leak.


perrya (author) on November 19, 2020:

Depending on the age, some cars needs an adapter for the fitting,

BRENDA ARLEDGE from Washington Court House on November 18, 2020:

I have done this before and it is very easy if your vehicle is equipped for it.

I had to get something put on my van that I had at the time so I could do this, but it works great.

Sure saves the expense of having it done.

Liz Westwood from UK on November 18, 2020:

Thos is a very helpful article. A garage would charge a premium for this service. Leaks in AC though can be a real headache.