AC Problems on 300D 78

[muybweno]

well summers around the corner and i want to see if i can get my AC to work just by doing the work myself....thats if i'm smart enough!

anyways got problems with my AC.. it wont give me any cool air whatsoever. I'm kinda confused about the AC system in the first place...

1. When i turn on the AC with dial turn all the way down to the blue and let it sit for about 5 minutes...i get extremely hot air....just like if the heater was on.

2. When the system is in this position, The compressor switch is on "off". When i turn that on while its blowing hot air, the engine doesn't lose RPM's like it should...but instead, it makes the blower motor run a little faster (you can hear the difference in air blowing into the car)

3. I cant see anything through the little glass peep hole in the dryer/reciever canister. My service manual told me to look in there to see if it shows signs of bubbles in which case i'm running low on freon....I dont see anything at all.

anyone know what might be the problem here? where should i check first?

any help is gladly appreciated