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Old 05-17-2021, 12:32 AM   #1
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Hey all,


Starting to get hot here, and I discovered that my AC wasn't working. Figured on a 25 year old truck it probably just needed an evac and recharge, so I took it to a shop. Guy said he recovered basically no refrigerant, vacuum test failed, and when he refilled it, it just started spewing out of the high side connection on the passengers side at the front of the condenser. I opted to fix it myself, and he ended up charging me about 70 bucks basically to identify the leak. I understand why, and it's less than I think I would have paid elsewhere. That said, I'd rather not pay $70 per leak if there are more problems.


So my questions are:


- Should I just go ahead and replace all the O-rings I can easily access preemptively before taking it back? The one I took out on the front of the condenser was pretty crusty-looking -- maybe an indicator of the condition of the rest of the seals in the system?


- Are there any other parts I should consider replacing before getting it filled? I understand that the "dryer" ("liquid tank" in the FSM?) in AC systems is often supposed to be replaced if the system is depressurized. I don't know how depressurized the system was or for how long.


I'd much rather spend a few bucks and some time now to get everything up to snuff before taking it back for $200 worth of service and refrigerant, than to burn that money, have to buy and replace the stuff in a month, and pay it again. That said, if the o-ring I replaced is the one that always fails and the other ones will likely be good for another 10 years and the dryer is probably fine, I won't waste my time.


Any insight is appreciated!
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Old 05-17-2021, 01:29 AM   #2
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Anytime the system is opened the accumulator/drier should be replaced, would not be a bad idea to replace the O-rings while the system is discharged. Make sure the O-rings are designed for AC refrigerant, ones I have are green.


If the compressor was being replaced the expansion valve as well as the drier should also be replaced at the same time, many auto parts stores require both these parts to be replaced to keep the warranty on the compressor, some require all 3 to be on the same receipt.


For your repair, you can just replace the drier, reason being when the system is opened the drier material ( desiccant in the drier) becomes exposed to the atmosphere and can absorb moisture which is the worst thing you want in the sealed AC system, one of the reasons why a vacuum is pulled on the system ( to remove any moisture and to check for leaks).


If you buy an aftermarket drier it most likely will not have the site window that the service manual shows, I have not seen any aftermarket ones with the site glass that the OEM part has.
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Old 05-17-2021, 01:50 AM   #3
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If you buy an aftermarket drier it most likely will not have the site window that the service manual shows, I have not seen any aftermarket ones with the site glass that the OEM part has.
I got lucky on the Napa Temp/Four Seasons one I got for Hector - it has the sight glass. However, I understand the glass isn't really necessary with R134 systems.
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Old 05-17-2021, 01:30 PM   #4
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I have a 1998 Frontier, in Phoenix, 256K miles.


I say to replace the drier (don't worry if the new one has no sight glass, not so useful with R134a) and the leaky O-rings you've discovered. I wouldn't replace "all O-rings", most of mine are factory except on the high pressure line I replaced a few years ago (pinhole). Yes, must use special O-rings for refrigerant use, oftentimes green. Auto parts stores sell as a kit (or individually at NAPA/CarQuest).



NEVER ADD ANY SEALER OR REFRIGERANT CONTAINING SEALER !!! UV DYE IS OK.
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Old 05-22-2021, 02:23 AM   #5
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Thanks everyone! Planning to do the drier but not the expansion valve, as it seems that's usually necessary only when the compressor blows up. Still hoping to do the O-rings that are fairly convenient at least, and especially on the high pressure side. I'd kind of like to know what size they all are before I get in there though, especially considering how distinctly not-o-ring-shaped the one I already did was. I have a small kit from O'Reilly, but some of the sizes are really close together. My local Nissan parts was kind enough to send me a system diagram with reference numbers, and I've managed to figure out a couple of sizes and most of the actual Nissan part numbers. The FSM also has a cryptic single-number "O-ring size" that doesn't make a whole lot of sense. I'll post the docs I have in a few minutes when I figure out how to do pictures...


Anyone have any more insight on what the actual sizes are, or should I just wing it, and go with what fits?


Planning to get the drier mounted, but leave it capped and ask the mechanic to do the last two hookups right before he hooks up his machine.
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Old 05-22-2021, 03:12 AM   #6
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^Results of my sleuthing so far


^Picture from Nissan Parts with "Reference numbers"

^Relevant page from the FSM. Note cryptic "O-ring size" designation for each connection.
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Old 05-23-2021, 03:11 AM   #7
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Weirdness...


Started replacing o-rings and discovered that some just straight weren't there, while most of the others were black. Not sure if the OEM ones are black or someone just went through and put in buna-n or something. I noticed some wrench marks on the fittings, so my suspicion is the later. Both sides of the evaporator were missing o-rings altogether, and both the FSM and the doc I got from Nissan says there should be something there. Went ahead and put in what fit. I'll upload the table again with the sizes filled out when I'm done.


Other thing I noticed is a fair amount of green oil in the fittings. How much oil should there be in the system? It wasn't like it was dripping out or anything, but there was definitely a little pool in each fitting when I opened it. Especially in the compressor ports. Is this something I should be concerned about? I know the amount of oil in the system can be a bit tricky to get right as it's really hard to check unless you're replacing the compressor or something, but does this sound normal?
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Old 05-23-2021, 02:13 PM   #8
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Quote:
Originally Posted by delangle View Post
Other thing I noticed is a fair amount of green oil in the fittings. How much oil should there be in the system? It wasn't like it was dripping out or anything, but there was definitely a little pool in each fitting when I opened it. Especially in the compressor ports. Is this something I should be concerned about? I know the amount of oil in the system can be a bit tricky to get right as it's really hard to check unless you're replacing the compressor or something, but does this sound normal?

Does not sound atypical. Yes, the amount of oil can be tricky to guess, and i pretty important, just have to do your best.
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Old 06-01-2021, 01:41 AM   #9
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AC blowing cold again, thought I'd encourage people to do their own AC maintenance! Don't be intimidated. It's super doable, and you can rent the gauge and hose set and the vacuum pump for free at O'Reilly or probably other places (free meaning $130 + $170 deposit). Only issue is if your system is still pressurized you should get a shop to recover what's left and save the earth.


It's a pretty fun process, and this video lays it out very clearly. Only issues I had were the O'Reilly gauge/hose set didn't come with the can tap, which I had to buy separately and they wouldn't take on return, but it was only 7 bucks and they did have it on the shelf. Also, the video either used a different can tap or the guy didn't understand it. All the way clockwise is open, counterclockwise is closed. You don't need to back it out like the guy says. This means you'll also loose whatever is in the yellow line when you switch cans, so you need to bleed the yellow line each time you put a new can on, not just the first time like he does. Check your FSM to see how much PAG100 oil you should add depending on what maintenance you did (page HA-49 for '96 D21 at least). Don't blow it all out on the first bleed though.


Hope this helps someone! Stay cool!
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Old 06-01-2021, 01:23 PM   #10
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Quote:
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This means you'll also loose whatever is in the yellow line when you switch cans, so you need to bleed the yellow line each time you put a new can on, not just the first time like he does.

Yes, for best results, any air in the lines must be purged. Yes, that uses a little refrigerant. I assume each can will actually deliver 10 to 11 oz. into a system, as besides purging, not all the refrigerant gets pulled from the cans (even if warm - not hot - water is used to warm up the cans).
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