Just retrofitted my 89 sub from r12 to 134. I put 8oz.s of ester into the compressor and hand turned it since it had not been run in about 2 years ( the system still had some pressure until I broke the line). I have added about 30oz.s of 134 and the compressor is cycling on for 3 secs and then off continuously. Its also quite hot to the touch- like 2 Mississippi's. I changed all of the orings and put in a new orifice tube. The old orifice wasn't even that dirty even though it has never been changed. The pressure on my gauge draws down to about 40psi when it kicks in. But when I turn the a/c switch off and the compressor stops it shoot up past 90 psi. Ive stopped adding 134 at this point because the compressor is getting too hot and sound has also changed- it sounds rougher with more vibration than it did before. Do these compressors (Harrison 928, R4 or R6- not sure) usually run hot? Im not sure why the pressure builds so high when its not cycling either. And, yes Im adding 134 to the low pressure port! Taking all suggestions!