It always takes time before the A/C comes out cold. That is normal. When the temperature gets hotter outside, the air conditioner cannot blow out as cold of air as when it is 20 degrees cooler outside. There is a
limit on the change of temperature drop of air entering and air leaving the evaporator coil. Also the hotter it gets, the condenser coil has a harder time giving up the heat that it has picked up. If you have to add refrigerant, you must have a leak. Larger leaks cannot be fixed by just adding more refrigerant. The leak must be fixed. With small leaks, adding more refrigerant might last a month to a year before it leaks back out again.
Yes, they work, and they are "user-friendly." But that's only true if your system is otherwise okay. The gauge only checks the low pressure side of the system, not revealing other possible problems than a small leak. If you have a compressor problem, or a blocked orifice tube, or any other problem on the outlet side of the compressor, you won't know it without using a full gauge set. Still, it won't hurt to try one. If you need more than one can, you probably should have it checked, since you very likely have other problems. Leaking a couple of ounces a year isn't a big deal, but more than that indicates bigger troubles.
answered 2 years, 3 months ago
Worked like a charm in my 1997 Ford Explorer. The unit comes with a "dummy gauge" to prevent over filling. The instructions are easy to follow, and the total repair time was about 10 minutes. Note: I did need to purchase an additional can to get a "full charge" reading on the gauge. That was three months ago, and my Explorer has been transformed from an oven to a freezer (it gets very VERY cold when I turn the AC to high). Compared to the $100 I was quoted by pretty much every local auto repair shop just to look at the AC system. I fixed it for half that. . .