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): 
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:
- Which connection to use? The top one or the bottom one?
- 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.
Best Answer
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!