Freon was low, the clutch would not stay in very long while trying to add the freon, I continued to put the freon in at a slow pace,after about 18 oz. the clutch did kick in and stayed in through out the process but,the pressure is still 20 low and 100 high with no cold air. I found oily residue around the low pressure switch and tightened it about one and one half turns which, may have been where the leak was.Was my system too low and should have I vacuumed first., or what may be the problem?

The clutch is engaged when you have power going to it AND there is enough freon pressure in the system. Check the freon level, if low add some and the clutch should engage when the pressure is high enough, like 50 to 75 psi. If you have pressure, check the fuse and electrical connections for a loose wire.

What is the pressure in your low pressure side at 80 degrees ambient? Did you use gauges?
U said the clutch will not stay engaged, meaning that it engages and then releases. If so, that means the clutch winding is good but that perhaps you have a loose wire feeding the clutch or a bad, intermittent relay. And if that is not the case then you are LOW in freon and the low pressure cut off switch is disconnecting the clutch when the pressure goes down. Pressure should be around 35 pounds on suction line at about 3000 rpm.

Does the compressor kick in when you turn it on?(if not it could be the a/c switch or the power to it, the a/c clutch wire connection, the clutch itself, or it's low on freon) You should hear the clutch kick in when you turn the a/c on. Low freon will also cause the clutch to not kick in. Remove the low-pressure switch plug and jump it with a piece of electrical wire. If the clutch kicks in, you just need to add some freon. Put the plug back where it was after you remove the jumper wire.
Is the belt on and adjusted to the right tension? If the belt is loose it won't cool as good as it should.
Check the freon in the system with a gage. If it's low, add some to the right amount and see if it cools. If it is overcharged, it will blow hot air, too.
The heater control valve slider should be all the way to the left so hot water isn't allowed to circulate through the heater core which would also make it blow hot air out the a/c ducts.
Good luck, they can be a pain, but with careful, step by step troubleshooting it can be fixed. There is plenty of information about a/c online to help you out. Try googling in: auto ac troubleshooting tips for more info. garcuda

Depending on how much freon is in the system, it could be a faulty low pressure switch or a faulty clutch.
You would jumper the low pressure switch to eliminate it for a test.

ADD Freon. It's a R134 system and the pressure is too low. Trust me add Freon and it will work fine. With a low amount of Freon if you jump the low pressure switch at the accumulator it will be very cold but will not have enough pressure to kick on the low pressure switch.

low freon soumds to me.. jump out the low pressure cut out switch near the dryer...or jump clutch relay in the distribution center. with clutch ingauged hook up guages to check low and high side pressures... also easy trick go to auto store get a can of 134a freon with hose and add the can the clutch should stay inguaged longer and longer as you fill the sytem... with clutch inguaged rev motor up to 1500 the guage on the hose should be around 35 to 40 pounds if low add more

if the clutch is worn and when the a/c works, it works OK, then the clutch gap is excesive and will need to be adjusted. you cant put freon in without the engine running, the low side pressure will be too high. get the compressor running first. if it cools ok, then dont add freon.

You can buy a can or,refil kit of R-134-A at walmart however only put the freon in on the low side (read the directions) if the freon gas will not go in; run an 18 gauge wire from the battery to the compressor clutch switch to run the compressor if the freon gas still won't go in it must be evacuated and, recharged by a shop. only put in enough freon to get the system cold any more than that and, you will lose cooling again (over charge)

use 134A and you can put it in your self.. Just pay attention Only instal freon in the low side of your system.. low side is always the larger hose ... Got that ? larger .. small hose is high side is not not the place to put it in .. Find your largest air conditioner hose and follow it out till you find a port to put in freon .. which you can buy it and the hose at a walmart store..they do make a sealant also that will sometimes slow the loss of freon.. let me know if you need more.. jerry

Before you add Freon, you should check the leaking first, if the Freon is too low, sometimes cause this kind problems. use color Freon test it and tight the leaking area and then add Freon, you can not do it yourself because the law say.