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Slow fill on A/C

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    Slow fill on A/C

    I have a 1995 chevy K1500 with 5.7L engine. Put A/C system back in vehicle, vacuumed. After 2 hours it still showed -28 psi so I put in the r134a refrigerant.
    Took about 3 hours to get the 2 lbs in. Final reading was 40/225. I didn't check the ambient temperature but it was near 80. Had blower on high, system on max and windows open. Should it take that long? Only thing not replaced in system is the evaporator.

    No, it shouldn't. -28 psi? we'd all be dead! 28 inch's ok. Your pressures are a bit high, with the slow intake of refrigerant, it make me wonder if your service connections are good and if there is still some air in the system. If your connections aren't good, all you see on the gauge is what happening in the hose.
    225 on the high side is around 138 deg condensing temp, rule of thumb for air cooled condensers is no more than 40 deg over air temp passing through the condenser, you are closer to 60 over. Also low side is too high.


    • Ringer
      Ringer commented
      Editing a comment
      I guess I meant 28 in HG vac. I went out to check it again and now showing 0/25 so It all leaked out. Have to fix that first. I figured holding a vacuum for 2 hours it was okay. At that low of pressure I don't know why the compressor is still engaged when ac is turned on. What's the best way of measuring the temp at condenser?

    High side pressure is the temp of the refrigerant at the point of condensing. Look in the ref section of this site for 134a temp/pressure chart.
    A thermometer in front of the condenser will tell you the temp of the air passing through the coil.
    A system that hold with gauges attached (if in fact the connection is getting though to the system) and leak with the gauges off also points to bad service valve connections.
    P.S. don't post a comment to what I wrote, post a reply. Posting comments don't show that new material was added to the thread, a reply below it does. Below this reply should be a box you can type in and will be a reply to what I wrote.


      Oh, ok. I didn't see the reply button, Sorry about that. Man, those service valves are brand new, of course that may be why it takes so long to fill. I have a leak detector coming in friday so I'll get some leak detector.


        Some valves don't "play well" with some hose ends. I've had that happen esp with retro fit adapters. I've heard that some GM products use a "ball" in the valve in place of a Shraider (tire valve type) valve, and they can leak.


          I am really messing this up. I went out there to take the gauges off and the quick disconnect on low side just fell off. That's why it was reading zero. I got it back on and both sides show 30 even when running and now compressor isn't kicking on because of low pressure. I checked all the connectors to see if any oil leaked out and didn't feel anything. Like I said I have a leak detector coming in and will get some uv leak dye into it.


            Don't leave the gauges connected when not needed, they can leak, Pop them on when working on the system and remove. Put them back on if you need to test a day later.


              Good advice.


                You'll know performance while driving this, center vent output temp if 80s F real air temp should put out ABOUT 42 to 45F if any humidity in around dew points will drip water - quick open hood see just damp return metal accumulator on to compressor.

                BTW "measuring vacuum" is commonly said as inches of mercury or symbol Hg. That's the pressure of area right where you are midline normal @ sea level is 29.92Hg for example. Factor your altitude can for A/C use be maxed out 1Hg higher (dial gauges) per 1,000 ft. Some weather could show minute differences all things the same.

                Temp coming in? If over dark pavement, sun, no monster fan blowing at the vehicle temps creep up, a lot and pressures of system accordingly.

                See that chart the sensitivity of temp and pressures it's helpful to understand what to expect.

                Good luck IDK why the slow port is/was way too slow should have quit to find out why? Port or hose end it's one or the other perhaps both? OE in these low port a Shrader high could be a ball (OMG put top quality OE grade cap back on virtually all leak!) GM declared the cap was the final seal!

                Future service for those just use low port this era touch and feel high return (can burn you AYOR) do the chart that's the pressure like magic.

                Hey - soon after this truck many other vehicles quit making a high side port as just another place to leak!

                Best tests will be keeping a thermo in center vent watch it while driving vs speed on recirculate even when/ if mid 90sF stays in the 40s you are good. I own a '97 worked on many same the weak link is lousy fan clutches OE all thermostatic, 5 blade fan good for a few years goes weak - all did and new was worse (cloned junk) so watch engine temp stay the same all the time as your guide almost no exceptions or find out why it's off if it creeps up even a little,
                MetroWest, Boston


                  I got the leak detector in and was putting in the dye. I had to bypass the low pressure switch to get the compressor running. It still had 20 psi in the system. The gauge reading after putting in the dye was zero on the low side and 80 on the high side. The line running from condenser to evaporator was coated with ice. This was after only 10 minutes of running. I'm going to check with the leak detector but is this showing a restriction on that line?


                    I guess it could have froze up since I had low refrigerant in it. I checked all over the system and didn't find one leak or see any green with the ultraviolet. I ran the ac and checked the vents and no alarm. Does it have to be running for me to check it?


                      ? Leaking fast has to show up maybe hear it, bubble test.

                      Hmmm "you said No alarm at vents" suggests you used a sniffer - fav of mine will sniff out just a cap held with finger away from vehicle or tests with common butane lighter. Can also pick up stray things learn it and settings.

                      Run finger (everything off) under lines connections and a good look at condenser may have to take top parts off.

                      Hate to waste refrigerant if/when cooling oil is moving with dye now slower ones stain or make an oily puddle of water, has to be humid enough and working a little while.

                      Bit early drain tubes if found should be clean - no oil now dye.

                      Underside compressors at + behind clutch rebuilt or not shut off and sniff there.

                      "O" tube you should see on condenser remove the right front directional lens - just look O tube is there.

                      IDK connections at accumulator and once was green and red seals at compressor are different thickness would hear that if wrong.

                      Right now this is leak finding seems system can work.

                      You should see evidence dye or not clean area if suspect spot is dirty see it come back. Last - careful jumping switches even year '95 low might be OK if just 2 wires AYOR if 3!

                      Blow out valve I think was rear on compressor wire to it held by snap ring has to seal, those could vary design - some used some just a dummy plug in case it's required come with a plastic one or last ones did you saved one from the old compressor IDK each brand, clones or all OE state by state laws?
                      MetroWest, Boston


                        Originally posted by Ringer View Post
                        I The line running from condenser to evaporator was coated with ice. This was after only 10 minutes of running. I'm going to check with the leak detector but is this showing a restriction on that line?
                        The line from the condenser to the evap in a normal system should not be cold, is this one with the orifice tube in the condenser?, if not, it looks like you have a clogged condenser outlet line.


                          From the condenser, where the orifice is located, to the evaporated was frosted over the whole length.


                            Ok, that is different, if the orifice is in the condenser then it will start boiling in the line, and cooling it.


                              Would that mean the orifice is plugged up? I guess not if the liquid was getting through to boil along the line.
                              Last edited by Ringer; 1 week ago.


                                Found leak around bolt that holds compressor in. Used sniffer. Couldn't see any dye so I'm pulling the compressor. Before I did that I had it running (accumulator low pressure connector was bad and not activating compressor, so replaced it) about 100 psi high side but low side went down to 10 psi and line to evaporator from orifice in condenser frosted up. Line from compressor to condenser was hot enough to burn your hand on.


                                  Found leak - great. Pressures don't mean a lot till it's properly "full" not over or under by too much for this.

                                  High side should be ABOUT 2.5 times the temp in F. With a raised idle say 1,500 +/- so if air coming in is 100F you'll see 250 PSI.

                                  Low on this CCOT system will or should read at accumulator about 40 PSI the vent routing adds about 5F even on recirculate it draws in fresh air - lots of it or you'd suffocate. Look at door jams for the fresh air vents don't plug those new law for US OMG was around 1968! GM blowers early never totally shut off - ticked folks off.

                                  Just remember pressure do NOT tell you amount in a system only measured in to a well held vacuum does,
                                  MetroWest, Boston


                                    Pulled the compressor and green dye was around edges of seal. Followed track of dye: Went into low side to compressor, out compressor to condenser and that was it. None at other end around orifice. Orifice had a black lint like coating on it. Blew air through condenser so orifice must have been the restriction. I guess I need to put new evaporator, compressor, condenser and orifice in. While I'm at it may as well replace liquid low pressure line.


                                      Go for it. It's had the "black death" a nickname for compressor that went out, debris blew thru system and can again and again.

                                      Check or toss parts, items that hold debris and many don't flush out.
                                      Good news it's a truck so parts should be available, reasonable cost just not thrilled with quality of much of anything many cloned things just one can wreck the show.

                                      Warranty can and require proof of accumulator done each time or not cover the job. Read and save info on what was done if it fails again.

                                      Good luck and do spread oil upstream of compressor for new start ups and bench spin new compressors with oil that first few seconds of it running matters a lot!
                                      MetroWest, Boston