Those kits can work, if used as an interim fix (until you make repairs) or if your system has just lost it's punch over time without any leaks or mechanical problems (a vacuum test can confirm that) ..... if used cautiously.

As others have said, the only perfect way to charge the system is to evacuate, vacuum for a period (to check for leaks) then recharge with the correct amount of R134a/PAG oil.

That being said, sometimes you're in a jam and need a quick fix to get you through a trip.

So, if you must charge from a can. Buy the freon that already has the PAG oil in the can with the freon (typically when you loose freon, you loose oil as well and the ratio of freon to oil must be kept accurate for the system to function well). Avoid cans that also have a leak sealer.

Connect the can to the low side, turn the A/C on high fan speed, recirc. on. Place a thermometer in the center vent and try to keep the engine running above 1000 rpm. As soon as the temp in the center vent stops rising, close the valve on the can. You do not want to overcharge R134a.

DEWFPO

--
1998 S90 071,245 and 1995 964 154,100