I kind of have the same problem with my 1990 Ford Mustang 5.0.(with manual 5 speed)
I serviced my AC this summer as well and did it properly. I evacuated old freon and filled it with proper amount of freon and oil (as the pressure is right on).
Whenever I have my fan on (with the AC OFF) the stupid AC pump cycles ON and OFF repeatedly. It would be no big deal but it also does it when I'm idling at a stoplight waiting for it to turn green. Occasionally my car dies because of it.
Big pain in my ass and even embarrassing at times.
How'd I fix my problem?
I just unplugged the top plug + wire going to my AC compressor. Now it can't cycle on and off lol.
It might not be the right way to do it - I'd be interested to see what is - but its fast, easy, and FREE.