Be careful with how much you put in. Total system only holds approx 2lbs. When you plugged back in and it worked, that meant there was a decent amount in the system. 18oz is a little over half the system. W/o pressure gauges on both sides and the FSM that gives you a chart of high/low you won't know the correct level of freon based on the temp and humidity.
I thought mine wasn't working well enough, but then read the FSM and it'* very thorough and interesting. Technically it'* only supposed to be about 20F cooler from the vents than external temps and humidity plays a large factor in that too.
00 Regal GS: All kinds of cool stuff.