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Is PAG Still Needed?

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    Is PAG Still Needed?

    I've lost all of the refrigerant from the system in my '99 Nissan Maxima resulting in a non-operational compressor. One AM, it worked perfect ... that same PM it blew warm but the compressor cycled ... the next AM nothing.

    It's apparent that the system rid itself of all refrigerant over about 24 hours.

    In doing my initial visual inspection of the system, I inadvertently depressed the relief pin in the low side service valve and not so much as a hiss was heard, telling me the system is empty.

    I did the UV inspection thing (totally dark garage, UV light, super-awesome yellow glasses), from the top and underneath the whole AC system.

    Due to a previous repair, dye is already in the system.

    The only place where dye was seen was inside the low side service valve.

    Both the low side and high side service valves have since been replaced and system is holding vacuum perfectly.

    Based on the fact that I have not seen any evidence of oil loss, with the recharge of the system with refrigerant am I correct in my perspective that no oil needs to be or should be added?

    Is this to say you accidentally pushed the low side Schrader and heard a hiss? Just that you think it's low by the sound ? Not enough you first should have had the cap on that so no mistakes and take the pressure vs the ambient temp at least know if it's close to same in pressure as the temp in chart below tells you it has some or if lower than chart call it essentially empty.

    Chart, hope it shows >

    That's very telling and if low A/C will quit blowing cold and eventually stop engaging compressor. How much if significant oil loss remains unknown unless you started from known zero all over again or an educated guess by a mess it might have made. IMO is you can add 2oz. if you are pretty sure it's not already overloaded with oil and do mark it and keep track.

    The real problem is why it's low still? Showing dye where you pushed the pin would show dye so that's not convincing yet unless you actually can also see bubbles with soapy water there or sniff it out then FIX IT as it could be the whole reason.

    Vacuum and see if that holds for at least 1/2 hour a couple even better then fill it to specified amount exactly see how it works or not at all and go from there.

    Can be elusive for shaft seals to leak and not show oil evidence or somehow oil wasn't near there when it leaked down while not engaged possible.

    In short - find out if it's really low and fix why if so first then move on based on results of that,
    MetroWest, Boston


      If it leaks out over the course of a season, you MIGHT get away with not adding oil, but it is a gamble, if it leaks over the course of a day, you ARE going to need oil. If you don't add enough you are going to kill the compressor in short order.


        Still thinking? Same day it works then nothing but UV dye seen on the port touched anyway so my guess is the real problem hasn't been found. This may not be a leak at all there are tons of other reasons for compressors to quit which is why at a minimum a static pressure is needed.

        The long held idea was OK to add a couple if a known leak fixed but we aren't there yet or did I miss something which is possible? If when you are convinced it's too low to work and can't find it the tricky ones are back side of condensers that would be unusual and too soon to see stain, evaporator was too fast might show oil in the drain spout should be dry as a chip. Shaft seal of compressors if somehow is blew when not running (maybe) let refrigerant out and not oil was there to lose.

        Need to check multiple ways if refrigerant is the issue most of the time A/C quits is because it leaked but NOT all the time, know that,
        MetroWest, Boston


          OK men ... here’s what’s transpired.

          As as stated above, both service valves were replaced.

          With respect to the input from the pros provided above, I’ve vacuumed the system several times and the system appears to hold a vacuum perfectly. After proper vacuum pressures were reached for no less than 45 minutes the system holds vacuum for 24 + hours ... I’ve gone through this process twice and each time no loss of vacuum was observed.

          I started the prcoess of charging the system this morning. The compressor triggered and ran throughout the process but low side and high side pressures disappointingly stayed quite low (20 - 30 psi low side), (no > 50 psi high side). Ambient temp was about 82* F.

          I found refrigerant oil leaking from the high side service port from the connection of my gauge set quick connector and the service port.

          Based on all of my previous findings indicating a tight system, does anyone think I’m off-base by thinking I still have a service valve failure or is there some other failure that I’m missing that will cause this?
          Last edited by Bumperquip; 05-19-2018, 02:59 PM.


            I’m wondering ... guys ... if I didn’t screw myself up.

            I’m wondering if I didn’t adequately purge atmosphere from my charge/supply hose.

            Once my refrigerant can was pierced and the valve opened, I did crack the supply hose connection at the manifold for a second or so but is there some a physical sign that the hose has been properly purged ... like the escape of mist, telling me the hose is filled with refrigerant?



              Bummer finding new valve leaking or this could be the gauge connector? Hard to know for sure so far to me. Oil seen now we are talking oil and the guess how much plus verify that leak as the source I'm not totally convinced it's the initial problem but is to be dealt with now. Just note this also about "holding a vacuum" is that at sea level the expected PRESSURE of atmosphere is just 14.7 PSI is what is trying to get into a vacuum or zero via air not refrigerant not totally the issue but to think of. If leaking it could leak just OUT now static pressure is or should be much higher than that 14.7 chart shows if just a few ounces remain would be 90 PSI perhaps just sitting there at 82F add some pressure for engine heat.

              Yuk - the 50 high side stayed low or no time during the charge even reflected much higher pressure with compressor engaged.

              It's your $$ now but this game isn't near over yet to be sure damage isn't involved! Hate to say I'd begin now with seeing how much can be recovered OUT of the system vs known amount charged in before the final decision know if it ran way too low all that time simply pouring out refrigerant when you thought you were adding isn't good.

              IDK - I would have added first measure a known amount into the vacuum without the engine running yet will quit taking in more and be equal to the source at some point. A chart I have shows this car with any engine only uses 25oz 134a total charge isn't much and 6.75oz PAG-100. Verify that with sticker on the car or other sources there's no assurance those specs are correct even some replacement parts along the way may change the charge - beware.

              Reading back the problem happened first then both valves replaced first thought this was a sudden 24hr. leakdown from working to inoperative? That's not very consistent with even a bad valve with a good cap on it so what's the timeline and story there?

              Here's my concern so far: The gauges are just not up to par or working and or new valves aren't working properly now the guess only is you touched the low port pin before gauges thought the hiss alone meant low pressure means nothing to me you needed a pressure.

              So if it can't hold it's not going to work or be filled knowing the right amount is in it.

              Back to how it died: It's not fair but compressors will keep trying AFTER they can't condense refrigerant which is imperative to carry the oil or the compressor if brand new can and will burn right up for lack of oil.

              If that happened you'd never get a good high pressure of any significance like you just posted even if it was enough of a charge for just a while.

              An outside last still guessing is use of the gauges wasn't understood how and where to have each for readings and what position for charging throw in they just don't work properly either remains unknown.

              Now what? Check the gauges on something and other fittings vs known ones that work high on this list. Not so sure I'd want those gauges on a vehicle I wanted the A/C to work in about now they could be the problem so I have to suggest another set of gauges and your call AYOR do this yet again with known gauges on those fittings that switched which wasn't behaving probably replace them both again knowing they are right as best you can.

              Not an enviable situation at all for you and is difficult to know for sure now just where this problem stands,

              MetroWest, Boston


                Your new post showed before I was done so out of order now I can't change. So, you are using the small cans presumably 12oz and didn't purge the hose to can to clear the line. You should be able to with the vacuum pump BTW but the little bit of air isn't the problem just don't do that again. I totally doubt there's enough air in just hose to cause this problem,
                MetroWest, Boston


                  Mr. Tom,

                  First ... much obliged for the replies.

                  I think what my first order of business will be is to replace my manifold gauge set with a set that includes manual lock-down connectors (instead of the quick connects) and an installed purge valve.

                  Second, have the system evacuated.

                  Third, replace (again) the offending service valve.

                  Then, start all over.

                  One thing you’ve mentioned several times and that’s been a question of my own is the quality and integrity of my gauge set.

                  My really suspect that that is an issue.


                    Good luck. I too doubt the gauges first. Always have two sets if another is needed compare them with each other. This is a tough nut over probably some foolish flaw just way too bad how much else can go wrong over so little really.

                    Just a suggestion with mostly common A/C here. If it isn't blowing cold and warm enough to know it is learn what to do to disable it so it can't try till you have time and the weather to deal with it. Reason is most vehicles will cycle A/C off season even nasty cold with the defrost or mix setting just seconds or more all depends IMO is exercising it off season would normally not stay on pressures would quickly plummet but if seriously low which isn't much in this and many damage is happening for lack of lube and you aren't aware till in season.

                    My sign off says my location can expect it cold MOST of the year not needed for me personally at all on my own vehicles now plenty old will disable them if any doubts. Some luck involved too the primary two I use are all original the newest was built in 1996 nothing for repair known since new! Smile but you can't know if it works and does go well below zero where I am it's not going to work nor would you know it. Surprisingly just engine heat if parked after a run even that cold I can hear compressor cycle just seconds now this old don't allow it for the several months just know you aren't messing anything else up if you do that yourself when this is all solved,
                    MetroWest, Boston


                      Thanks again for the assist.

                      BTW, I’m in the Tampa, FL area so A/C is quite important mostly year round.

                      Ive maintained my own vehicles for decades and have restored a couple/few ... I quite enjoy it and tend to trust my own work far exceeding my trust in others.

                      However, auto A/C is the one area I have not had a ton of experience in and I’d really like to get a grip on it.

                      I can’t imagine I won’t be back in the next day or so with more Qs.


                        Understood. Trouble is that even the simpliest A/C systems you have a lot to understand now these twists with failures that aren't proven to me/us yet the precise fix it's making this more involved all by itself for just this bad luck. Long run something wrong about refrigerant amount and oils can just make it a constant issue or come back again with same issues.

                        Of course you need it but you decide how far you are willing to go to get the best useful and dependable life out of it. It's just not a very forgiving area of automotives nor very cheap at some point. Think hard on what your options are so this doesn't end up a $$ pit for just A/C for you,
                        MetroWest, Boston


                          I've been pondering/obsessing on this issue.

                          Give me some input on this ... and this is assuming that my tools are working properly.

                          Is it likely that a system that holds vacuum and shows no leaks, can't hold pressure? I mean, is it possible that the high side service valve that has been replaced and showed no sign of a leak under vacuum would fail under compressor pressure?

                          Yesterday, notwithstanding the the failure from my recharge effort, I wanted to the see if the system had depressurized itself over the course of a day or if it were holding any pressure.

                          I connected the gauge set (all valves closed) and the car and compressor remained off.

                          My gauge set read 50 psi on the low side and 50 psi on the high side. This is a low side pressure increase from when I aborted my recharge session which was 20 - 30 psi at that time (with the compressor running) and the system had not been run since.

                          I guess my questions are these:

                          If I have a leak in the system, why would the system still maintain these pressures?

                          Is it possible that a leak is present and vacuum is still held but the leak becomes evident under compressor pressure?

                          If the system is intact, what would cause the discharge of the oil (and refrigerant) from the high side service port during recharge?


                            Yes - things, A/C seals anywhere included can leak under pressure but not under vacuum as said earlier was only holding 14.7 PSI of pressure OUT of the system in the opposite direction of force on any seals.

                            Please first really get to know your gauges and what pressure are reading like it that the system or the source. Refrigerants (look back to the chart and understand that) are and have to be very temp/pressure sensitive and condense (change from vapor to a liquid) in this case at reasonable pressures. Your tires hold pressure too I'm sure you are very familiar with. More trivia: Air in a silly tire you are checking static pressure which Is what I want you to do. Side note for tires and air which is temp sensitive also will increase pressure by about 1F or each 10F increase in temp always say to set them while cold not after like a highway run.

                            That similarity stops there refrigerants under pressure become a liquid and must then evaporate at the right time and spot is what makes it work. Technically that is "removing heat" from passing air not adding cool same to you, you feel cool/cold air blowing out vents.

                            So far you haven't achieved any credible pressures so lost like you are. Stuck to verify those gauges and if the new ports are damaged or just no good for some reason? You said you saw an active leak with hose attached that messes up the whole show to start all over again.

                            Goal is to know how much refrigerant you have added into a well held vacuum the primary reason moisture can't exist in a vacuum it would turn any liquid if that bad into a vapor and remove the vapor. This is done at reasonable temperatures I believe we have with this not trying to mess with something with below freezing air temps not much would be working or credible.

                            Also know that while a small can especially is discharging into the vehicle's system that little can will get cold must be kept warm by hands or water or would be equal pressure as system in no time nothing moves either way. Some gauges would push pressure back to source if you were doing it all wrong so have to know your gauges and stinks but also know even if new they work as intended! OMG that would mess up the show.

                            That's where this is to me unfortunate circumstances and lack of credible info/pressures along with multiple tries is the reason your subject line asks about oil and yes it's unknown how much is lost plus if you don't know this car from new totally just another thing to guess at that it wasn't butchered up along the way.

                            The end all when oil info or contamination is known or the guess so difficult you really need to flush the system out and know if debris is involved which parts cannot be reused new or not stinks and puts a failure back to square one again!

                            It's just not very forgiving for failures or mistakes.

                            Unsaid so far I think: Do beware of the snake oil fix-it tricks sold all over the place are never likely to work and ruin things much more often than fix anything but sell well and get away with claims that simply are NOT true. I feel for you it can get costly for this note just do be as sure as you can of everything and understand it or the risk is there to make it worse way too easily,
                            MetroWest, Boston


                              Welp ... the only reason I'm not going to continue this in my own garage is because I don't own a recovery unit and my system needs to be evacuated of the inadequate charge that remains in the system.

                              After doing more reading and talking with the shop guy yesterday, I'm pretty convinced that my oil discharge issue that resulted in my project abort the other day was the result of a faulty gauge hose coupler or maybe user error on my part.

                              Nonetheless, the car goes to the shop this Thursday morning for some confirmatory diagnosis and hopefully a full system recharge.

                              I'm a bit disappointed as I hate having to bail for assistance but I'm not sure, if purchased, I'll use a recovery unit often enough to justify the cost.


                                Quite likely the right choice is bail out and pay the equipment will out do any savings in many cases. Recovery wouldn't be needed if know empty again as I've said can be known if pressure is lower than temp if you trust both the pressure and accurate temp right at the system's parts there' s nothing there or just heat of plain air if engine was run?

                                I don't recall you ever seeing any respectable pressure from a running compressor when thought there was enough refrigerant in it bugs me? Question if it's already toast remains unknown to me so far.

                                Anyhow - good luck with a correct fix and it lasts for you I know you need it where you are. Been there (Sarasota) in August for a couple weeks just 5 miles inland + family in LA in season now choking humidity that just doesn't do it where I am.

                                It's nobody's fault, A/C quickly gets not DIY friendly or cost effective,
                                MetroWest, Boston


                                  Originally posted by Bumperquip View Post
                                  Nonetheless, the car goes to the shop this Thursday morning for some confirmatory diagnosis and hopefully a full system recharge.
                                  I'm a bit disappointed as I hate having to bail for assistance
                                  Same with me, I don't like to go for professional help. But sometimes a job is too involved for me and my skill set. Like upcoming shower re-do and laminate stone-look flooring (I've done engineered wood floating floors, but what I read indicates these are more involved and complicated).


                                    I'm the dumb-a**, but then again, there is some equipment I just don't own i.e. a refrigerant recovery unit.

                                    The shop found my fix and my system to be sound.

                                    My previous oil discharge was related to a crappy gauge set coupler, as I suspected.

                                    The system was evacuated, holds vacuum nicely and was recharged and re-oiled by the shop.

                                    However, I'm told that the high side pressure was a little high and this is attributable to ... ... ... a failed e-fan.

                                    All pretty good news but honestly, I could have found that.

                                    Lesson learned.

                                    Now I want my own recovery/recharge unit.