Hi all,
I have a 1987 Chevy G20 van 5.7L K van TBI that I inherited so to speak. The AC did not work and this is a requirement to live in hot nasty humid south Florida. This is a cargo van that did have a conversion and a rear ac that I pulled out and brought it back to just the original front AC only. The compressor a Four Seasons R4 did have a shaft leak so I replaced the unit with a new reman unit. Although I would have loved to buy a new one, the one they stock (advance auto parts), does not have the correct fittings for the manifold hose. I replaced the nasty orifice tube and sealed up everything else tiiiiight. Anyways, I also in the process performed the conversion to 134a and spent much time blowing oil out of the lines and taking all but the evap out to clean and blow and clean and blow more. Dropped in 8oz of oil in pump and lines with dye I then vacuumed out the system for a little over an hour. I then charged the unit with about 3.0 lbs of 134a. It was about 93 degrees outside so I charged the system to what my dad recommended on the low side to 38 lbs on fast idle but what I find very odd is that the high side pressure is now at 275psi. Dude, is that normal? Is this going to blow up this new r4? I am not sure that this sounds correct or not. It is blowing cool but since I have no idea how cold this unit is supposed to be and the fact that I converted it if this is normal temps or not. My 2000 Nissan on High is about 200psi and that is what I would have expected and freezes your nose off. If you are familiar with these converted R12-134a older 80's AC orifice tube units I would love to have some feedback on the pressures.

Second is that when you determine pressure against the temp charts is that for the surrounding air or maybe the temp on the condenser? I am just curious as since this is a full size van it sort of has a insulating effect since the engine is pretty much buried into the vehicle.

Third question. The new r4 compressor was pretty hard to turn by hand. Which from what I understand is pretty normal when new. When I run the AC though the RPM drops down to 625 and it seems like the engine is struggling as it shakes slightly like the compressor is dragging too much? However when I hold gas down a little everything seems ok. Doesn't the ECM bump up the idle speed when AC is kicked on? How can I diagnose this? Is the compressor too stiff? Too much high side pressure maybe? Or is there a component that is now not working? I did reset the timing and when I pull the blk/tan wire for dist reference the rpm does drop to 500 so I can imagine that the IAC is working correctly.

Also I noticed that the whole time the AC was on the compressor never cycled on or off. Can these older R4's run 100% duty cycle like that or did I miss something?

I wish that I could have seen how this beast worked when it was new so I would have a little more knowledge about its performance and capacities.

Sorry for all the questions but just need to hear from a few experts!

Thanks!