Yes, mine hisses.

Yes, mine is hard to turn. My A/C works. (You say you only use it occasionally. You should try to run it weekly for a minute or so, to keep the lubrication up to the compressor etc.) I've often thought at playing with a push-button bypass switch to turn it off and on, and just use the A/C control for temperature adjustments. Should work, but I've not tried it yet. I only think about it when driving, and when at home, forget again.

The hissing sound, though, could be a vacuum leak. When I first got mine (18yrs old), it hissed a lot, but all the time. Turned out that the hose from the manifold to the vacuum accumulator under the dash leaked badly at the connection. Also, 2 or 3 of the little black hoses from the push button control assembly to the dash vents were in bad shape and one was missing altogether. If yours are off, the switch and hoses are numbered, though hard to see in the dark of under dash. I have a "map" of where the tubes should go if you need them - came from Paul Seminina, I think.

Alan