Just wanted some opinions to make a decision. The o-rings on top of my AC compressor on my '98 LT are going bad as I have oil on the top of my compressor and have to recharge every 3 months or so.
An HVAC tech claimed I could bleed out the system and have about 10 minutes or so to replace the o-rings and close the system without having to vacuum. Not sure how true or if I want to do this. It's getting summer here in Missouri and days of low humidity do not exist until winter time.
In a nutshell I'd rather be safe and rent the vacuum-but is this true what the HVAC guy said? It'd sure be convenient-but I'd rather not run the risk of getting moisture in the system because I'll have REAL problems. Thanks for reading.

 

For what it's worth, on my 04 when I first bought it (going in knowing it had a locked up compressor), I replaced the compressor, condenser, accumulator, and all the lines, flushed the evaporator with a flush-can from the parts store, blew it out good after the flush with an air compressor, bolted everything together (the compressor was pre-oiled), added in freon to the low side port with a cheap hose and gauge from the parts store, and have never looked back, that was about 3 years ago now, still blows ice cold.

NOT ONCE have I vacuumed the system to remove moister (and I live in Florida mind you, was doing all this in the beginning of summer whrn it's about 90% humidity on average...), and or check for leaks. I did have one bad o-ring after install; ran great for about a month, then all the freon leaked out, rather quickly I might add. I opened the system BACK up, replaced the o-ring, recharged again with the same cheap hose and gauge and over the counter cans of R134, and everything has worked beautifully since then.

After the successful AC repair on my Blazer, it's hard for me to believe all these "technicians" who most of the time just want your money to do the service, tell me that all these steps have to be made with special equipment or your going to have catastrophic failure... Just use common since; don't open the system up to service it if it's raining. If you're going to have the lines off/open for any amount of time, put some sort of plug or cap on them to keep debris out. If all you're doing is replacing the two O-rings (which are more like washers with rubber discs pressed into them...), you'll literally have the system open for maybe 30 seconds. One bolt, lift the block that has the lines on it, pop the old O-rings off, wipe both surfaces down with a clean cloth just to clean off the sealing surfaces (being careful not to push crap INTO the compressor or lines of course...), lay the new seals into place, then reinstall. Recharge with R134a and enjoy. Personally, I would not bother with vacuuming the system.

HOWEVER

With all that being said, a vacuum DOES help you if you have one to see if you actually sealed the system... Let's say those O-rings are not the only ones leaking; only 2 ways to find out. 1) vacuum the system and see if if holds vacuum; if it does, then you fixed the leak. 2) charge it with freon and see if it leaks out anywhere else or it holds... Personally I find it more convenient to just charge the system and hope for the best lol. Some will argue "well you're possibly just wasting money on freon if it leaks out"; compare the cost of a few cans of freon VS what that tech is going to charge you to vacuum test the system and tell me which you prefer...

my $0.02

 

I have access to a vacuum-my apartment maintenance guy said I could use it and a set of gauges.

Had I read your post this morning I probably would have went ahead and just broke the line loose and put those new o-rings in. But since I have access to a vacuum at no cost it probably wouldn't hurt to go all out. My Blazer is a '98 and the AC didn't work when I bought it. Didn't know if all the pressure had gone or not as it worked fine after I charged it. Looks like new compressor was put in around 2006 as the date was written on compressor. I added a can of oil last year not knowing if it needed it or not. Is there any way of checking oil level?

Like I said I'm gonna go all out and vacuum out system and check for leaks with the gauge set I have access to. It isn't scorching hot yet but I'm definitely going to have ice cold AC before that happens. Nothing better than having cold AC while driving home after being outside in the heat all day-and nothing worse than not having it while stuck in traffic. Thanks for your thoughts and reply.

 

I did replace those o-rings last spring and used the vacuum my apartment maintenance guy let me use. Couple of months ago I noticed it not blowing very cold and finally compressor won't come on period. Thought it could be shaft seals on compressor but nope-I see tiny bubbles coming out around the lines on top of the compressor right around the very seals I replaced last spring. All I can think of is a piece of debris got lodged in it as I was tightening it down or a defective o-ring. It's too cold outside to do anything with it but it's driving me nuts. When I now something is wrong I HAVE to fix it...just the way I am.
Read of people putting in cans with the sealer and never having problems. I seem to get a mixed bag of opinions on this. My other problem is my compressor has a light film of oil from the leak over it. How in the world can you now if there's enough oil in the compressor?

 

There are a lot of moving parts in this thread, let's see if I can help with some of it.

Once a seal is leaking you really need to replace it. I work on residential, marine and automotive AC as well as refrigeration and have never used a stop leak product. I wouldn't want that stuff circulating through my systems but with that said, most of the 134a cans in the auto parts store have stop leak in them. You may have some in your system now. Most auto AC systems have a low pressure switch so there is limited stress when the system leaks its charge but that's not the way to maintain these systems.

The system has a certain spec for total oil. It gets distributed throughout all of the components. There are charts for how much each component usually holds so when it gets replaced you replace that amount of oil. Alternatively for some components like the compressor or accumulator you can pour the oil out of the old one and replace that amount. The charts are more accurate for things like the condenser which are harder to drain. So you run a virtual tally of oil puts and takes and try to stay at the target level. Finding oil around seals and connections helps find leaks as you have pointed out but unless you have a catastrophic and instant purge, the amount of oil lost with small leaks is generally not significant. On major work, the entire system gets flushed and you start over but most DIY'ers are probably not doing this.

The reason for evacuating before charging is threefold. Remove moisture, remove other non-condensables (air), and prove that the system can hold said vacuum. If you can't hold a vacuum there is either a leak or there is still moisture in the system that keeps boiling off and raising the pressure. Because of this dry nitrogen is used to pressure test for leaks and start the purge of the system contaminants and then you vacuum test until you hold a vacuum. Without the vacuum step as is advocated by the poster above the system has to deal with moisture and air or nitrogen. If the accumulator is new then a good one can deal with small amounts of moisture to clean up the system but nothing with remove air. This changes the system pressures, reduces efficiency and in some cases can break the compressor. The poster above and in other threads advocates a non vacuum approach and it apparently works in his case. He may or may not be sweeping the system withe refrigerant to purge most of the air first, I don't know. It's not the right way to do AC work and it's illegal to intentionally vent refrigerants into the atmosphere and violations carry a heavy fine and in at least one high profile case - jail time. Also the EPA pays a reward to rat people out. Everyone has to make their own decisions on how to do their AC work but at least be aware of the law. In addition, any professional working on AC has to have an EPA license, vacuum pumps, reclaim machines and canisters, etc to ever attach a gauge set so they don't have a choice. Most reputable outfits won't violate these rules and fly straight or they may not be able to make a living, and plenty of them don't like some of these rules.

George