QuestionI have an 87 F 250 w/ 6.9 Diesel I have worked on the ac several times and can get it to blow cold for amonth or two. I recently had comp fail and did the whole deal, flush and vac and fill. This system has been converted to 134a, also did the whole deal. Any how, the question I have for you is, as follows. The system requirements are 7 to9 oz of oil, 52 oz of refrig, i installed 8.5 PAG direct to comp on install. Ran engine up to 1500, started filling system at 36oz I had about 32 on low side and 250 on high side. I added another 12oz got to 40 low and 350 high, I then idled down to street idle and pressures went through the roof. I had 60 low and well over 400 high, at which point I shut down ac pressures equalized. I then released a little and got low down to 50 and high came down to 350. I am cocncerned I have something wrong. Pressure seems very high. This system has red orifice if that info helps. Please let me know. I would also like a place to find average numbers on this system, as I got no where close to the recomended charge of 52 oz.
AnswerHello Corey,First Corey the system is overcharged.Did you changed the accumulator?.The pressure should be 25 to 35psi on the lowside / highside should be 190 to 210psi.
total oil in system is 8oz. Evcuate the system for at least
45min to 1hr. Be sure the radiator fan clutch is working properly,if not, the a/c pressure on the high side will climb.When you charge, add 2lbs of freon-rotate the compressor hub about 10x and then start the engine.Cycle the compressor on and off for 3sec. intervals 4x and then
leave it on and monitor the psi readings. add another .75lbs., and watch readings/ let the system stabilize.Over charge systems can damage parts.R134 psi runs higher than r12. good luck davidt
