98 Freightliner century AC not blowing cold

And turn can upside down

 

Ok. Verify that clutch is kickin in, cause pressures that low with clutchbengaged should put your low side close to a vacuum

 

Look on the firewall for a tag. Add that amount. Probably around 3.5-4lbs. max. Can’t go by the gauge on the can. Low pressure can be anywhere from 35-55lbs. Once the correct amount is added, going by weight. If after adding correct amount by weight, the gauges read too high or low, and still blowing warm. Then you got a problem. Must go by weight. 5 cans at most outta do the trick. Keep cans upright. Upside down, you may split compressor open.