On a recent trip i had this problem. I was on a ship and had a carrier reefer that had a bad smv valve ( would only open 27%). I didn't have a spare on board so I took the valve apart and removed the piston as the manual said. Well while trying to adjust the temp with the suction service valve i encountered the following problem. The discharge pressure would go so high that it kept opening high pressure cutout switch. I had the suction valve almost closed then the pressure would go almost to the cutout limit and then back on and of while the temp would go down only during the period when the discharge pressure was going from high to low while average temp was going slowly up. I noticed that the quench valve kept closing and opening all the time. Now i always thought that when the smv is fully open the quench valve is suppose to remain shut. I keep wondering what did i do wrong and what was the problem.