A/C clutch on 1977 Regal shuts on and off...

I just bought a nice little 77 Regal from a 87 Y.O. woman, whose son was selling it for her. The car had basically been off the road for 4 years (started every few weeks for 2 years, then the battery died 2 years ago, and son was too cheap to buy one, thank God it was in a garage) To sell it, he had just put a battery and a little gas. Anyway, he said the air worked, then a few days before I got up there, he said he had the car running in the driveway, and the A/C stopped blowing cold . So, when I got up there, the compressor would try to come on, run about 5-10 seconds, then stop for longer than that. Did this for a few minutes, then I just turned it off. He thought it still was R-12. He had 1 whole can. Thought I would likely need more than that since the clutch wasn't really engaging
Anyway, It really got hot here in Atlanta, and I had just sold a 1973 Lincoln Mark lV with working air, and Dad's car (he's 84) air doesn't work, and it was in the mid 90's all of the sudden, so...I needed to do something quick, that wasn't too expensive. I did a search for Freeze 12 and Duracool (Stuff I used years ago) but the search took me to Amazon and something no one seems to have heard of before, Red Tek 12a. Took a chance and bought some since the reviews seemed decent.
Since it's been a very long time since I messed with adding "Freon" I went with the stuff to a friend who used to work on home A/C's awhile back. Had to get some fittings from O'Reilly's to go from R12 to R134 type (they only had one in the kit) Was going to try to keep this short, failed...So, he put the stuff in, almost 2 cans. (much less product in the Red Tek cans) And the A/C is quite cool! But, the clutch still shuts itself off, especially when the revs were up. My friend has had older cars in the past, but hadn't in decades so he kept trying to tell me, oh, that's perfectly normal, that's what they all do. I sure don't recall any other a6 compressors doing this (both my 1973 Lincoln and my Dad's 1979 Continental have these compressors too) I thought it was the later smaller units that cycled on and off? The pressure was fairly high, but supposedly in the safe area via the gauge (80 PSI I think?) but I seem to recall their info was it should be in the 30-38 PSI range.
I know, should have had the the system evacuated (it's so funny, the company that makes Red Tek will say it mixes great with R12 or R134, and elsewhere they will say, don't mix it) I needed air fast,(and was just taking the buyer's word for it that it actually was just working) and while I have it, I think something has to be wrong. I sure don't want to damage the compressor. Or am I wrong, that revving the engine will make the clutch disengage temporarily ?
Doesn't seem to be low on oil, it's quieter than the compressor in my 73 Mark IV was, and it lasted the 10 years I owned the car....
Any thoughts, suggestions? Thanks!

P.S. I was thinking about using this stuff in my Dad's Lincoln, compressor is fine, but condenser had a leak...I can't seem to find condensers for sale like you can compressors. Will I have to look into having it repaired?

 

Dont mix refrigerants. When the factory does it its called blending. But anyway dont do it. Find the pressure switch, pull the plug and jump it out. if the cycling stops its a pressure issue or the the switch is bad. 80 psig on the low side is WAY to high unless your running R22. 30 -38 is good for 134 - R12.

 

Well, went ahead and had the system evacuated (only $15 man, do I feel stoopid, thought it would cost way more, wish I did that first!) then put in 3 cans of Red Tek 12a...not as cold as it was before (must have had a little R12 still in there) but the compressor runs all the time now, which is nice when it's 90+ every single day of the week...