Is that the same sensor that the temp gauge is reading from? or is there an additional sensor?
I think you may be onto something, assuming that the shop where I had work done on the hoses (new one fabricated) did the r-12 load correct as they evacuated the R-12 and said I was in fact a little heavy and the high pressure cutoff was being tripped. After they recharged the cooling was noticeably cooler at the vent.
But this new symptom is that the compressor clutch stops engagement. Also read RN newest flyer and Robinson was talking about worn clutches and that you have to remove a shim to compensate for wear?