20 years ago I had an old refrigerator compressor that I harvested from a mini fridge someone put an ice pick through the cold plate of trying to defrost it. I put fittings on to use as both a vacuum pump and a recovery unit into an old R134a recovery tank. On my old stuff I recycled the refrigerant and never worried about it. My total investment including manifold gauges was under $150. That compressor eventually siezed and I harvested another from a ac window unit that had leaked out all its refrigerant from corrosion in the condenser. Still use that for recovering refrigerant. I bought a vacuum pump from Harbor Freight 15 years ago and it still functions perfectly. Replaced the compressor on my G35 two years ago when the clutch coil failed at over 200K with excellent results. I vacuum for atleast 30 minutes on a day thats over 80°F and up to an hour if its 60°F. The goal is to remove all the moisture to prevent hydrofloric acid. You want to purge the hoses before you admit refrigerant into the system to remove the air and moisture from them. I generally pull a vacuum, once the vacuum time is up and its in a deep vacuum, close the manifold valves and turn off the vacuum pump. I let it sit for 30 minutes to make sure it holds vacuum, then hook up the charging source. Open the charging port and either push on the schrader under the manifold set or slightly crack the hose fitting until refrigerant comes out. At that point, open the low side valve and let the system equalize to the bottle pressure. Now close the low side valve, start the vehicle, turn the ac on to maximum cold and maximum fan speed and select recirculate. Now you can slowly admit refrigerant until the a/c gets cold, the compressor stops cycling, and the pressures are within range. Generally speaking most of the systems I mess with are modified and cannot be charged by weight. Stock systems can and should be charged by weight. An accurate postal scale is how I do it. Charging from small cans is possible, but not ideal as it is impossible to get all the refrigerant out of one and you have no idea how much esacpes from each 12oz can. Once I get the system where I want it, I close the source bottle valve, close the high side valve at the high side port to isolate the high side line from the system, then crack the high side manifold valve to allow the system to purge the high side service hose. Once the gauges are in equalibrium with the system, close the low side service valve and remove the charging hose, screw the service caps on and done. I refuse to use rental hose sets because people vacuum black death systems and also tend to get dirt and debris in the hose set, something you do not want in your system.

 

20 years ago I had an old refrigerator compressor that I harvested from a mini fridge someone put an ice pick through the cold plate of trying to defrost it. I put fittings on to use as both a vacuum pump and a recovery unit into an old R134a recovery tank. On my old stuff I recycled the refrigerant and never worried about it. My total investment including manifold gauges was under $150. That compressor eventually siezed and I harvested another from a ac window unit that had leaked out all its refrigerant from corrosion in the condenser. Still use that for recovering refrigerant. I bought a vacuum pump from Harbor Freight 15 years ago and it still functions perfectly. Replaced the compressor on my G35 two years ago when the clutch coil failed at over 200K with excellent results. I vacuum for atleast 30 minutes on a day thats over 80°F and up to an hour if its 60°F. The goal is to remove all the moisture to prevent hydrofloric acid. You want to purge the hoses before you admit refrigerant into the system to remove the air and moisture from them. I generally pull a vacuum, once the vacuum time is up and its in a deep vacuum, close the manifold valves and turn off the vacuum pump. I let it sit for 30 minutes to make sure it holds vacuum, then hook up the charging source. Open the charging port and either push on the schrader under the manifold set or slightly crack the hose fitting until refrigerant comes out. At that point, open the low side valve and let the system equalize to the bottle pressure. Now close the low side valve, start the vehicle, turn the ac on to maximum cold and maximum fan speed and select recirculate. Now you can slowly admit refrigerant until the a/c gets cold, the compressor stops cycling, and the pressures are within range. Generally speaking most of the systems I mess with are modified and cannot be charged by weight. Stock systems can and should be charged by weight. An accurate postal scale is how I do it. Charging from small cans is possible, but not ideal as it is impossible to get all the refrigerant out of one and you have no idea how much escapes from each 12oz can. Once I get the system where I want it, I close the source bottle valve, close the high side valve at the high side port to isolate the high side line from the system, then crack the high side manifold valve to allow the system to purge the high side service hose. Once the gauges are in equalibrium with the system, close the low side service valve and remove the charging hose, screw the service caps on and done. I refuse to use rental hose sets because people vacuum black death systems and also tend to get dirt and debris in the hose set, something you do not want in your system. This is a 200K mile a/c system with a new replacement compressor cooling on a 105°F day. It can be done and properly done should get ice cold.

 

Will also add for anyone interested in being able to recover and save $$$$ on refrigerant. I have a filter/drier and pressure gauge in-line on my recovery apparatus. Pressure gauge to prevent from over pressuring the bottle was salvaged from an old manifold set that the hoses were in sad shape on. The filter drier cleans the refrigerant and removes moisture. It is fairly inexpensive, disposable and easily changed.


A proper recovery tank is relatively inexpensive. Since my fleet includes 3 vehicles with rear air, anytime I have to open the system I would lose 3-5 lbs if R134a or pay to have it recovered. Its against federal law to vent it.