My freezer is apparently slowly leaking refrigerant. I sent it in for repairs a few years back, but now it is failing with the exactly the same symptoms: compressor working non-stop, temperature never goes to -18C (it has a digital display), but stays around -11C. It has developed this condition very gradually.

My freezer has two screw-on connections (I think they were added during the repairs): one on the stump pipe going out of the compressor (bottom), and the other on the little stump going out of filter-drier (top): enter image description here

My plan is to buy an auto air conditioner refill kit (gas can + gauge + tubes), and just add some gas. My freezer uses just 120g (4.2oz) of R-134A, so I know the gas is compatible, but I need to add just a little bit.

My questions:

  1. Which connection to use? The top one or the bottom one?
  2. How can I know I added enough?

I know this is not really a fix without fixing the leak, if it helps for just a few months, I'm good with that.

  • This seems like a bad idea.
    – Tester101
    Mar 8, 2016 at 0:44
  • @Tester101: could you elaborate what could go wrong? Except that I'll need to refill again as I didn't fix the root cause of the issue?
    – haimg
    Mar 8, 2016 at 6:09
  • 1
    You could damage the equipment and/or yourself. My advice when it comes to working with refrigerants: If you don't know what you're doing, you shouldn't be doing it.
    – Tester101
    Mar 8, 2016 at 13:56

5 Answers 5


The filler hose for the small cans only fits on the low pressure side.

The high pressure side should have a different fitting. This is how cars are anyway. So it is impossible to connect the refill can to the high side with the refill kit you buy at the auto store.

The small cans don't have enough pressure to overfill the system. So you can't overfill it. You could put the can in a bucket of warm water whole filling that will help get all of the refrigerant out of it.

Make sure it is running while you are filling it.

Good luck!

  • Thanks for answering! So which one is the high side and which one is the low side? My freezer has exactly the same connections on both pipes.
    – haimg
    Mar 8, 2016 at 0:42
  • If they put the same fitting on both sides then you would have to connect a set of refrigeration gauges to the fittings to determine which is high or low. Usually the low side has a big fat quick disconnect fitting on it. From you picture the one on the top looks larger to me. But then I can't really see it that well. Take the black plastic caps off and see if they are the same.
    – ArchonOSX
    Mar 8, 2016 at 0:54
  • Those little cans can overfil a refer as you don't know how much Freon is still in the system. The stub is usually on the low side and a small fridge takes less than 6 psi using r134
    – Ed Beal
    Jul 13, 2018 at 14:43

Answering the second part of my question:

Freezers and refrigerators actually use very little refrigerant, and it's important not to overfill them. I found the low pressure tap, and it was in -10 psi vaccuum while compressor is running, which confirmed it for me that the freezer didn't have enough refrigerant.

I slowly added refrigerant till the low side was around 3-4 psi. It took surprisingly little gas, and the can is still nearly full. The freezer went to -20C within an hour, so it obviously worked.


I just refilled my GE Arctica refrigerator and followed YouTube demos. Filled the low pressure side pipe (the larger of the two) by first installing a tap or bullet piercing valve: bullet piercing valve

Then attach the hose end with the piercing needle to a 12-16oz R134a refrigerant (freon). Follow the piercing valve instructions carefully as you don't want any air going into the system.

enviro cap r12-r22

When you have attached the bullet piercing valve properly, attach the hose with the 12-16oz R134a can (not yet pierced, mind you) to the r-12/r-22 fitting on the piercing valve. You may have to bleed the hose a little by letting some freon through - you will know as it will be a fog squeaking out of the hose. Then tighten the hose fitting.

from Amazon

Then just be patient. Run the fridge back on. Open the 12-16oz can all the way and turn the piercing valve about 1/4 CCW to open the line. The whole process may take an hour or two. When you see the needle about 4-6 (green zone) then you are done my friend. Good Luck!


The low psi line is larger of the two. Your schrader valves may be leaking , i.e. you are out of gas. Replace valves before you re-fill it. I don't think the auto and refridgerators are the same size fittings, not sure


Automotive refrigerant R134a has and additive that should NOT be used in refrigerators or freezers. Most refrigerators use around 4.75oz - 6.50oz of refrigerant. This is crucial and must be accurate. You can not be accurate when using a can. If you aren’t certified or qualified to work on refrigerators sealed systems then you shouldn’t. There are laws in place for many reasons. One good reason is so you don’t kill yourself. Be smart, don’t play around with things like refrigerants and other gasses that can cause serious injuries.

  • I asked this question 4 years ago. After I got some answers I "topped up" the freezer using R134a and using the pressure gauge. In these 4 years, I needed to top it up once again, and after 2 long-distance moves the freezer is still going strong. I believe your answer is not helpful, and is just spreading fear and misinformation: it's not against the law, and not particularly dangerous either.
    – haimg
    Feb 20, 2020 at 0:03

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