summer air conditioning tune-up

[qship96]

after much searching,I still am not sure the best way to tell if my ac needs recharging!blows cold air,but is it at peak operating efficiency?how to tell-if a tech hooks up gauges to monitor pressures,is that enough to detect a slightly undercharged system,or should i pay for an evacuation and recharge using a machine that weighs the r134? if i get the evac and recharge,what about the compressor oil,does that need to be replaced because of this procedure?someone please walk me through this process before i take the car in to get checked!the system has never been worked on,nor recharged since it left japan almost 10 years ago.

[elwesso]

You have the FSM, so print it out have the tech check it over with the manifold guages

Even easier.. do this.... Attached is the table for the ambient to vent temp... Get a thermometer and stick it in the vent... If it proves to be in spec, i wouldnt worry about it...

Follow the directions on this table...

However, evacuating the system and having a fresh charge of oil is going to be very beneficial, but look at it for mostly maintenance..... Should cost about $100 to get the system vacuumed, re-oiled, and recharged!

The blue sticker on the drivers side strut tower tells how much oil is supposed to be in the system...

[qship96]

if i get the evac and recharge,are they suppose to add new oil,or does the machine recycle the oil that it took out? how do they measure the amount of oil taken out,if so?see many unanswered questions still!

[elwesso]

The service manual is to be used not as a relic to have for fun!!!

They measure how much oil came out and replace it with the same amount.

[qship96]

wes,if the evacuation machine sucks out the refrigerant along with the oil,how is it measured,as the refrigerant is measured by weight-please someone who knows this procedure inside-out explain it to us!

[DAEDALUS]

The machine separates the oil from the gas. It dumps it into a graduated container that tells them the volume, which the inject back into the system before recharging.

[elwesso]

Qship

I just read the first 30 pages of the HA section.. Tons of informaiton in there and I bet that all your questions are answered in there...

[qship96]

no,evac and recharge procedure not explained in manual at all-why i am asking,and why i have never serviced the system yet- not comfortable with the little knowledge of doing it correctly- a tech i asked today said the oil in the system would not be affected by a evac and recharge procedure? q45techs advice on this would put many minds to ease!

[DAEDALUS]

The tech was lying. Read my post.

[DominickJ30]

after much searching,I still am not sure the best way to tell if my ac needs recharging!blows cold air,but is it at peak operating efficiency?how to tell-if a tech hooks up gauges to monitor pressures,is that enough to detect a slightly undercharged system,or should i pay for an evacuation and recharge using a machine that weighs the r134? if i get the evac and recharge,what about the compressor oil,does that need to be replaced because of this procedure?someone please walk me through this process before i take the car in to get checked!the system has never been worked on,nor recharged since it left japan almost 10 years ago.

R-134a has a shelf life of about 25 years, so the only reason for an undercharged system is a leak. There is no way to know for sure from gauge readings what state of charge there is, the only indicator is low static gauge readings. Below ambient temp.

I believe removing all the oil would be very expensive because the compressor would have to be remove and the lines should be flushed.

I would replace the dryer anytime you introduce air and moisture to the system. Along with fresh oil. After the flush they put vacuum on the system and boil off the remaining moisture.

Then after measuring by weight how much refrigirant was in there they can determine if it was low. I think the page wes posted should have specs for the amount of refrigirant to put in. Good luck. If the A/C blows cold enough for you there is no reason to worry. Especially since the car never had an A/C problem.

[qship96]

The tech was lying. Read my post.

thank you! why i have hesitated to service the system to date! what would reall help me and others is a total discription of how the procedure SHOULD be done,so us owners can interview potential shops,and be comfortable that they are improving their ac system,not causing its death{right jesda?}

[maxnix]

Read Q45tech's posts on the subject.

Flushing the AC system and replacing the drier is one thing few of us do, including me so far.

[DAEDALUS]

thank you! why i have hesitated to service the system to date! what would reall help me and others is a total discription of how the procedure SHOULD be done,so us owners can interview potential shops,and be comfortable that they are improving their ac system,not causing its death{right jesda?}

Well, let me step back and qualify my answer. Oil does get removed anytime you evacuate the system. All machines I'm familiar with allow the operator to manually measure the extracted oil so he can replace it. But of course I'm not familiar with all machines. For all I know, the newer ones might measure the oil and replace it automatically, without any user input. The more automated the machine, the more profit the shop makes. This would be a logical and seemingly doable next step. So the tech saying the procedure won't impact the oil level might just depend on who's point of view he's considering.

Recovery/recycle machines are so easy to use that there's not much to gain by talking to the shops about a straightforward evac and fill. Where the techs need to know their stuff is with the diagnosis of problems and being able to use gauges and various symptoms to diagnose things.

The evac and fill is simply removing the refrigerant and oil, vacuuming out the system, timing the vacuum hold, measuring and replacing the oil, and recharging by weight.

[3Q Jay]

hmmmm. still not obvious to me how the type-S is returned to the system. dump it into the suction hose [i suppose this would mean running the compressor for a while with only what is in it's 'crankcase'?] force it in thru the drain valve [intuition says it would run right back out again]??buy 'pre-mixed' 134a with type-S [haven't even seen this, just musing???]

[DAEDALUS]

You mean the oil? The system is under vacuum when the oil's injected. It can be sucked in from a graduated fill bottle or injected with a special plastic syringe. The fill fittings are the high points in the system; gravity keeps the oil in. Once the oil's injected the system can be vacuumed again to get out any air that may have leaked in, but it's probably not necessary. The compressor won't turn on until there's sufficient pressure, but it can be used to speed up the recharge.

[3Q Jay]

Hi Robert, yes...the oil. So. when under vacuum, then the oil can be sucked in thru the 'low' side (near the evaporator) service valve, using the manifold set valve hooked to [immersed in] the contayner of recovered oil?? sorry if i'm daft, just not getting the 'inject' part.more questions: ultra-premium maintenance is the theme here at NICO, does the oil not receive contaminants or anything that would make it less than desireable to re-use?and--i'm not following you on the re-vacuum after putting the oil back in [acknowledged that you said optional]. wouldn't re-vaccing suck the oil back out of the system again?thanks, your info is very helpful....

[DAEDALUS]

Who said anything about reusing the old oil? Fresh new stuff to replenish the old. Only the volumes have to match. Since the system is under vacuum, it doesn't really matter if you put the oil in the high side or low side, depends on which fitting is hooked up to (fits) the oil bottle. The syringe is just a plastic container with a plunger that is used to insert oil and/or dye. Doesn't really matter which device is used. I would consider a second vacuum on the system because I know that a tiny bit of air would get in there when I put the oil in. A tiny bit will also get in when I disconnect the fittings, but there's only so much we can do. No significant amount of oil will leave under vacuum because the system is nearly 100% evacuated already, and because the oil will settle down at the bottom of the system, away from the fittings. Kind of like sucking on an upright straw with water in it but which is sealed at the other end. The water isn't going anywhere.The reason oil is lost when recovering is because of the high pressure differential and because there is a lot of mass movement--the oil is swept up by the moving refregerant. But all in all, only a fraction of the oil is removed during the initial recovery; most is still left behind in the various components.

[3Q Jay]

got it.slightly different direction... the rx/dryer is the vertical cylinder near the condensor? anything special or interesting aobut replacing it (besides vacuum down for at least 1/2 hour afterward)?

type-S oil is 1-2 weeks from Nissan chemicals according to IoS. and its $20 for 40ml. approved substitutes? Mine is R-134a.

I'm thinking to invest in an a/c vac pump and do this right myself. unless, that is that you are equipped--in which case we could work a deal....

[DAEDALUS]

Yeah, the drier is the shiny cylinder near the condenser and the battery. Don't forget you'll need new o-rings for each disconnection. Nissan ones are a bit pricey but not outrageous. Generic green ones should work fine too. New drier should come with its own switch.I didn't even know Nissan had their own brand of oil. Seems generic R134a shop oil would work. Expect to recover a few ounces; that Nissan stuff will cost a LOT (30ml = 1oz?).I'm AC equipped, but only for R-12 unfortunately.

[3Q Jay]

thanks. yeah, looking around on line i found 3 different PAG oils: 46 viscosity, 100, and 150. now to determine which is the match for type-S.....

[3Q Jay]

check this out...

http://www.technicalchemical.c...3.pdf

type S looks to be 46 vis. dang--i'll have to get the 100 vis [type R] also, to service the alty.....

[DAEDALUS]

Great find!

[elwesso]

Now wait a sec.. I thought the drier wsa the thing up on the low side service valve on the firewall... The liquid tank, near the condensor is on the high side... Am I mistaken?

[qship96]

well,after talking to a few shops and not feeling confident that any were going to do the procedure correctly{minimum 30 minute vacuum,etc} i spent some time cleaning condensor,streightening out a few bent fins,removing bugs,etc........and went for a drive with a taylor digital temp gauge stuck in the center vents-results are-51.0 degree air coming out at max blower speed,set at 65 with recirc on at 88 outside temp with high humidity{60-70%}while driving 65-75mph-second test,same speed and outside temp the vent temp got down to 42.3F when set on 65 and blower forced at lowest speed,on recirculate-so it looks like system is operating near 100% efficiency after 10 years and never having been recharged? comments....

[DAEDALUS]

Now wait a sec.. I thought the drier wsa the thing up on the low side service valve on the firewall... The liquid tank, near the condensor is on the high side... Am I mistaken?

The manual is a bit lousy in that regard. But order a drier from Joe and see what he sends you. Most if not all AC systems in cars are nearly identical in general appearance and layout.

The Q's AC was out when I bought it at 9 years old, so I had Pep Boys replace the compressor back in '99. The rebuild just began to leak, but it still works. I also have an '85 firebird. The car's a complete piece of crap, but the AC blows real strong. Without maintenance, longevity is luck of the draw.

[elwesso]

Without maintenance, longevity is luck of the draw.

True!!!! SO TRUE!

But regarding the other things... Im surprised that they make NO mention of the drier. Lookin in the parts book, they have no mention of the drier or reciever or any other nomenclature we mention. Theres the liquid tank, flexible hoses and everything. It looks as if from the parts diagram when you order the drier you get the low side hose as well (its all one piece, the hose and little silver thing on the pass side firewall).. It would make sense that the drier is on the low side, and the low side service valve is indeed on the firewall... I thought the low side was where the liquid tank was, but I was wrong... I gave jesda some false information too!!!

Its hard to say, maybe dennis will chime in. but Jesda asked the guy at meineke and he said that the drier is on the low side, and he said it was that thing on the firewall...

[DAEDALUS]

AC systems are not unique to the Q45 or even to Infiniti. They have a common design and layout across most models for good reasons. Be wary of what grunts at national chains tell you. Ask to see his ASE AC cert or even his EPA cert. He needs to have at least an EPA cert to operate the machine.

http://www.familycar.com/Classroom/ac1.htm

EDIT: BTW, the '90 manual does label the drier as the "Receiver drier".

[John Nordling]

I'm late to this game, but what if your compressor seems to leak oil/ I've been working on a 90 Q for about 21 months, and it leaked oil out while it sat. I had it on the road for one week about two months ago, but it wasn't warm enough to test the A/C. If I understand what you are saying, the compressor will have to come off of the car, be sealed, and then new oil added. Sounds expensive to boot!

I hope I'm wrong, but if it leaks, how can you tell how much oil to add?

[maxnix]

I hope I'm wrong, but if it leaks, how can you tell how much oil to add?

If you rehabilitate the AC (sounds like your seals are toast), you can start from scratch and fill with the FSM recommended amounts.

[DominickJ30]

The RECEIVER/dryer is on the high side of the system. After the condenser before the metering device. On an orofice tube system the ACCUMULATOR/dryer is on the low side. Basically the receiver allows liquid through and accumulator only allows vapor through. The 'liquid' tank you refer to is the receiver.