[reekor]

You sound a little lost. The pressure in the system changes with ambient temperature, the hotter it is outside the higher the pressure. As your A/C runs and gets cooler the pressure of the low side should get lower and the pressure on the high side should get higher. When you did the convertion did you drain the old oil? If not you should have. Once the system hits an all time low in pressure on the low side it should not rise unless the compressor starts cycling off. It sounds like you may have a gummed up front orifice tube.

Originally Posted by Old Nuke ET

I just finished converting my A/C system from R12 to R134. I sucked it down to a good vacuum and held it for at least 20 - 30 minutes, then shot the system with a good brand of R134 that included oil and leak seal ( just in case). I have a R134 gauge set but I am having trouble understanding the results. I have ice cold (or nearly) air in the back of the van, but the front air is mediocre at best.

I am reading about 37 to 42 lbs on the suction and about 180 on the high side. It seems to me that the compressor should be cycling but the compressor seems to just stay on all the time. On top of that I believe that these pressures are too high but I can't find any good reference materials on the R12 to R134 conversion. If I leave it run at idle the low and high side pressures eventually creep up to about 45 on suction and as much as 230 on high side.

Both heat exchangers seem to have plenty of condensation dripping from them, I am using a box fan on high speed in front of the condenser to simulate driving speeds for incoming air. Although this is a 93, it is in really mint condition mechanically - only 64,000 original miles on the clock. When I cut the vehicle off I notice that it only takes a few seconds for the suction side pressure and high side to equalize at about 90 lbs. Shouldn't there be an internal check valve system or something that would prevent such a quick equalization? Pressures were taken with both the front and rear units on high fan speeds.

Could it just be the excessive heat build up in the vicinity of the front unit because the vehicle is sitting still (despite the box fan?). What should normal pressures be after a conversion? How many ounces would be a correct shot for this system? Anybody else done this conversion?