A/C question
04-09-2004, 10:33 PM
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A/C question
OK here's another question for anyone that's good with a/c systems:
I recently went in to have my a/c system leak-tested and lo-and-behold, they identified a leaking compressor and a compressor-to-evaporator line.
I bought a used compressor (Nippondenso, same as what's in there, with a warranty) and a compressor-to-evaporator hose new for $50 (!), and also picked up the other hose from the evaporator to who-knows-where (condenser I think) for an additional $50, figuring if one went bad the other one is probably about to go bad. I also got a new (rebuilt really) receiver / drier because someone said that they rot out and fail and should be replaced if you're doing this amount of work on the a/c system. . .
So now I have a mountain of parts, some free time, and absolutely no clue what the hell I'm doing. I've NEVER dealt with an a/c system (only owned one other car in my life with it, and I never had a problem with that one). Can I just bolt the replacement compressor in or does it need to have oil in it or what? I know the system is discharged (because of the leaks and the fact that the a/c does nothing in terms of producing cold air and there ain't jack in the sight glass), so I'm pretty sure I can just unhook and replace stuff - but what should I know before I get into this so I do it correctly and don't end up killing the new compressor?
I recently went in to have my a/c system leak-tested and lo-and-behold, they identified a leaking compressor and a compressor-to-evaporator line.
I bought a used compressor (Nippondenso, same as what's in there, with a warranty) and a compressor-to-evaporator hose new for $50 (!), and also picked up the other hose from the evaporator to who-knows-where (condenser I think) for an additional $50, figuring if one went bad the other one is probably about to go bad. I also got a new (rebuilt really) receiver / drier because someone said that they rot out and fail and should be replaced if you're doing this amount of work on the a/c system. . .
So now I have a mountain of parts, some free time, and absolutely no clue what the hell I'm doing. I've NEVER dealt with an a/c system (only owned one other car in my life with it, and I never had a problem with that one). Can I just bolt the replacement compressor in or does it need to have oil in it or what? I know the system is discharged (because of the leaks and the fact that the a/c does nothing in terms of producing cold air and there ain't jack in the sight glass), so I'm pretty sure I can just unhook and replace stuff - but what should I know before I get into this so I do it correctly and don't end up killing the new compressor?
04-09-2004, 11:19 PM
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You might start by looking at this site: http://www.griffiths.com/achelp/achelp1.htm
You really should take the car to a AC shop to have them remove any r12 in the system.
I assume you're going top use R134a, since R12 isn't really available. You'll need different fittings for the compressor. You can buy a conversion kit that contains refrigerant and fittings at any auto store. I think you're supposed to charge throught the ports on the compressor. Unfortunately, it's real tight in there. I could never get a R12 charging hose on the shraeder valve. You can buy an "L" adapter for easier access.
You defintely need to have oil in the compressor before you turn it. You have to use oil that is compatible with the coolant. You should drain any oil in the compressor and replace it with the correct amount of R134a compatible oil.
The drier has a dessicant inside, so don't open it before you need to. Also note that there is a pressure switch on the drier that deactivates the compressor clutch when there refrigerant is low. This switch protects the compressor so you might replace it unless you know it's good.
Once you get the system together, you have to pull a high vacuum on the system for 30 minutes or so to remove the moisture. This might be the time to take it to a AC shop to evacuate and charge the system.
There's a lot more stuff I don't know about, so before you tear into the system look into it carefully.
Best of luck.
You really should take the car to a AC shop to have them remove any r12 in the system.
I assume you're going top use R134a, since R12 isn't really available. You'll need different fittings for the compressor. You can buy a conversion kit that contains refrigerant and fittings at any auto store. I think you're supposed to charge throught the ports on the compressor. Unfortunately, it's real tight in there. I could never get a R12 charging hose on the shraeder valve. You can buy an "L" adapter for easier access.
You defintely need to have oil in the compressor before you turn it. You have to use oil that is compatible with the coolant. You should drain any oil in the compressor and replace it with the correct amount of R134a compatible oil.
The drier has a dessicant inside, so don't open it before you need to. Also note that there is a pressure switch on the drier that deactivates the compressor clutch when there refrigerant is low. This switch protects the compressor so you might replace it unless you know it's good.
Once you get the system together, you have to pull a high vacuum on the system for 30 minutes or so to remove the moisture. This might be the time to take it to a AC shop to evacuate and charge the system.
There's a lot more stuff I don't know about, so before you tear into the system look into it carefully.
Best of luck.
04-10-2004, 05:02 AM
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Thanks. . . I've read a bunch of stuff on the raging debate between R12 & R134 and my own amateur but researched conclusion is that it's probably safer & cheaper to stick with R12 rather than changing out a bunch of stuff and risking blowing up (another) compressor over it. If I can get the system leak-proofed, it really isn't that hard to find the old stuff, and as long as the discharging / charging is done by a properly equipped shop, it doesn't sound like an environmental problem either. I've got a shop here that'll gladly charge it with R12 for about $20, I just have to prove it's leak-tight first (they'll leak-test it for $50 first and then the charge is free if it's okay). I'm just so ignorant about a/c systems that I don't want to put the new compressor & hoses in and end up toasting it just on the drive over there to charge it! It sounds like the clutch will just "free wheel" and the compressor won't engage though due to the pressure switch (yes I saw that on the new receiver / drier, seems to be in good condition), although suffice to say I won't try to run anything until I get oil in the compressor and the system charged, so I guess I'm okay replacing the compressor & hoses.
I can just get R12 compatible oil and add the appropriate amount (I think I read 2 oz somewhere) to the compressor, right (or should the shop do this once everything is on & they're going to charge it, after vaccuming it out)? Am I totally in over my head here? They quoted me like $900 to replace everything (compressor, hoses, receiver / drier - cost of labor only and to test / charge it) so I'm obviously trying to avoid as much of that cost as possible, but if I'm just gonna end up frigging it up, I'll bite the bullet and eat the $900. I really would like to have good, reliable working a/c on this car before the ungodly hot summer months get here and I'm sitting in Mojave or somewhere!
Related stupid question - if I have to do it myself before the compressor goes on, where exactly do I add the oil? To the part of the compressor where the hose screws onto? Or just pass on it, figure the compressor won't run due to the pressure switch / clutch bypass, drive it over there and let the shop deal with it?
I can just get R12 compatible oil and add the appropriate amount (I think I read 2 oz somewhere) to the compressor, right (or should the shop do this once everything is on & they're going to charge it, after vaccuming it out)? Am I totally in over my head here? They quoted me like $900 to replace everything (compressor, hoses, receiver / drier - cost of labor only and to test / charge it) so I'm obviously trying to avoid as much of that cost as possible, but if I'm just gonna end up frigging it up, I'll bite the bullet and eat the $900. I really would like to have good, reliable working a/c on this car before the ungodly hot summer months get here and I'm sitting in Mojave or somewhere!
Related stupid question - if I have to do it myself before the compressor goes on, where exactly do I add the oil? To the part of the compressor where the hose screws onto? Or just pass on it, figure the compressor won't run due to the pressure switch / clutch bypass, drive it over there and let the shop deal with it?
04-10-2004, 07:28 AM
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I was in a similar situation last summer -- a leak-down test revealed a leaky line, I was low on refrigerant and the shope game me some $500+ quote for repairs. I figured R12 is relatively cheap compared to the repair cost, so I just refilled my system with refrigerant off eBay (at home, rather than at a shop -- you're supposed to get a EPA certification on-line to go this route). I used two cans of R12 and one can of oil. After one year, my AC system is still running just as strong -- so I guess I lucked out and my leak wasn't too severe. YMMV.
04-10-2004, 12:54 PM
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If you got someone who will charge it with R12 for $20, I'd let them do it. Last summer I had my system checked. Leaks around the compressor seal and the firewall. So I'd have to replace the compressor, hoses, and expansion vavle at a minimum. Then they want about $3 an ounce to charge it with R12.
Anyway, if you're going to take it to a shop anyway, let them put the oil in. Just be sure to tell them the system needs oil. They can inject it with the refrigerant. So just do the mechanical stuff and let them do the AC stuff.
And about that certification you're supposed to have. You have to give them a lot personal info so they can track you. And sign a statement that you agree to obey the rules and have the equipment to do the job properly. Since the equipment cost thousands of dollars, its clear that people doing it themselves at home are not going to do this. So you're really setting yourself up for enforcement actions by certifying. I doubt they'll come after anyone at this point, let alone a backyard mechanic, but you should know what's going before you jump into all this. And no, I'm not a "the goverenment is out to get us" type. R134a requires no certification and works well. BTW, I've read that the A/C industry is trying to get R134a sale restricted, too.
Anyway, if you're going to take it to a shop anyway, let them put the oil in. Just be sure to tell them the system needs oil. They can inject it with the refrigerant. So just do the mechanical stuff and let them do the AC stuff.
And about that certification you're supposed to have. You have to give them a lot personal info so they can track you. And sign a statement that you agree to obey the rules and have the equipment to do the job properly. Since the equipment cost thousands of dollars, its clear that people doing it themselves at home are not going to do this. So you're really setting yourself up for enforcement actions by certifying. I doubt they'll come after anyone at this point, let alone a backyard mechanic, but you should know what's going before you jump into all this. And no, I'm not a "the goverenment is out to get us" type. R134a requires no certification and works well. BTW, I've read that the A/C industry is trying to get R134a sale restricted, too.
04-10-2004, 01:34 PM
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I've got the certification, it's a complete joke to get it provided you have half a brain. The EPA pretty much works on a complaint basis anyway and they have much bigger fish to fry than a shadetree mechanic. The harder part is buying the R-12 since it's about 35 bucks a can or more for the small ones.
The big trick with converting to 134a is changing to a new barrier type hose. The 134a molecules are smaller and will leak through a regular hose over time. The other trick is only putting in 80-90% of the 134a charge that's equivalent to the R12 charge you would have put in since you're using it in a system originally designed for R12. It evaporates easier this way and better evaporation leads to colder temps in the evaporator.
You're legally supposed to change the fittings to the 134a type if you retrofit. Other than a shop not touching your system if you haven't nobody's going to do anything if you don't actually change the fittings. The biggest change in addition to the barrier hoses is just using a compatible oil since mineral oil isn't miscible in 134a like it is in R12.
Now with that said, I personally think 134a sucks compared to R12, aside from not being as cold, it's been linked to testicular cancer and causing seizures if it leaks. No thanks. Now there's plenty of alternates that advertise themselves as a drop in R12 replacement. Most of them are a blend of other refrigerants to achieve similar characteristics to R12. The problem is because they're more than one chemical one may leak and the other won't which means you have to evacuate the whole system and refill from empty to keep things in balance instead of just being able to top it off.
What I like to use is something called envirocool. It's actually a hydrocarbon instead of a flurocarbon. (Isobutane). It cools even better than R12 does. You can vent it to atmosphere without any concerns. The catch is, it's not legal as a drop in replacement for R12, it's only legal as a replacement in an R134a system. Of course if you "convert" to 134a first and never actually charge it with 134a then you could put in the Envirocool legally. It also works fine with mineral oil like R12 or the Glycol types that 134a requires. I prefer the mineral personally as it's a true oil. Yes the Envirocool is technically flammable as it's a hydrocarbon, but it's actually got a higher flash point than 134a does. In a house I probably wouldn't use a hydrocarbon refrigerant for that reason, but considering you're sitting on several gallons of gasoline in a car, frankly 16 oz of isobutane isn't much of a concern. I just wouldn't recommend it if you like to smoke in your car to be safe although it's got a pine scent added to it so you can tell if it's leaking.
Just do a web search for Envirocool and you can find a few places that sell it. Also I will mention that it's not necessarily legal to use in some states because of local laws about using flammable refrigerants. You're on your own there but it's not really something I'd worry about too much. It's pretty reasonably priced at about 8 bucks a can. I've used it for a while now and I think it absolutely works great, I'm not sure if it requires barrier hoses but I had new ones made prior to putting it in so I haven't tried it with the old ones.
If you want an alternative to R12 I highly recommend checking it out instead of 134a. Just remember you have to convert your system to 134a before putting it in
The big trick with converting to 134a is changing to a new barrier type hose. The 134a molecules are smaller and will leak through a regular hose over time. The other trick is only putting in 80-90% of the 134a charge that's equivalent to the R12 charge you would have put in since you're using it in a system originally designed for R12. It evaporates easier this way and better evaporation leads to colder temps in the evaporator.
You're legally supposed to change the fittings to the 134a type if you retrofit. Other than a shop not touching your system if you haven't nobody's going to do anything if you don't actually change the fittings. The biggest change in addition to the barrier hoses is just using a compatible oil since mineral oil isn't miscible in 134a like it is in R12.
Now with that said, I personally think 134a sucks compared to R12, aside from not being as cold, it's been linked to testicular cancer and causing seizures if it leaks. No thanks. Now there's plenty of alternates that advertise themselves as a drop in R12 replacement. Most of them are a blend of other refrigerants to achieve similar characteristics to R12. The problem is because they're more than one chemical one may leak and the other won't which means you have to evacuate the whole system and refill from empty to keep things in balance instead of just being able to top it off.
What I like to use is something called envirocool. It's actually a hydrocarbon instead of a flurocarbon. (Isobutane). It cools even better than R12 does. You can vent it to atmosphere without any concerns. The catch is, it's not legal as a drop in replacement for R12, it's only legal as a replacement in an R134a system. Of course if you "convert" to 134a first and never actually charge it with 134a then you could put in the Envirocool legally. It also works fine with mineral oil like R12 or the Glycol types that 134a requires. I prefer the mineral personally as it's a true oil. Yes the Envirocool is technically flammable as it's a hydrocarbon, but it's actually got a higher flash point than 134a does. In a house I probably wouldn't use a hydrocarbon refrigerant for that reason, but considering you're sitting on several gallons of gasoline in a car, frankly 16 oz of isobutane isn't much of a concern. I just wouldn't recommend it if you like to smoke in your car to be safe although it's got a pine scent added to it so you can tell if it's leaking.
Just do a web search for Envirocool and you can find a few places that sell it. Also I will mention that it's not necessarily legal to use in some states because of local laws about using flammable refrigerants. You're on your own there but it's not really something I'd worry about too much. It's pretty reasonably priced at about 8 bucks a can. I've used it for a while now and I think it absolutely works great, I'm not sure if it requires barrier hoses but I had new ones made prior to putting it in so I haven't tried it with the old ones.
If you want an alternative to R12 I highly recommend checking it out instead of 134a. Just remember you have to convert your system to 134a before putting it in
04-10-2004, 02:46 PM
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Thanks, there have been a lot of posts on this here and elsewhere and it sounds like the 134a is decent enough but tends to blow up compressors, hence why I'm going to just stick with the R12. Plus I have a "zero tolerance" policy for leaks of any kind on my car, I don't care if it's fuel, oil, air, vaccum, freon, electricity, or whatever. It ain't supposed to leak, so I'll just fix it.
I'll look into that hydrocool stuff though, maybe with one of those aftermarket compressors (forget the manufacturer) that a lot of people use that are more suitable for the 134 it'd be okay though. . .
The hardest thing is going to be replacing those darned hoses!
I'll look into that hydrocool stuff though, maybe with one of those aftermarket compressors (forget the manufacturer) that a lot of people use that are more suitable for the 134 it'd be okay though. . .
The hardest thing is going to be replacing those darned hoses!
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04-10-2004, 03:33 PM
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Actually with the Envirocool it's easier to compress than even R12 so on an R12 system it's still less load on the compressor itself. Seriously the only downside there is to it is the fact that it's a hydrocarbon and potentially a fire hazard.
My Geo Tracker (stop laughing, the little bugger is damn near bulletproof even if it is gutless and kinda silly in general) uses the exact same Nippondenso compressor except for a different pulley and the port adapter that bolts on the top. I've been running the Envirocool in that for a couple years with no issues whatsoever. It actually uses less engine power than R12 and definitely less than 134a since the hydrocarbon based refrigerant is easier to compress. For what it's worth Mitsubishi Eclipses also use this same compressor, I suspect a whole lot of stuff uses that particular Nippondenso compressor given differences between the 3 vehicles that I know for sure use it.
I promise you the Envirocool won't cause your existing compressor to fail any sooner than R12 will. If anything it's going to make it last longer. Look up the Envirocool website they've got the typical Q&A faq with all that crap answered already. This is of course assuming they're being truthful but having used the stuff myself, I think they are. One other nice thing with the HC based stuff is that you can skip the new receiver/dryer. The HC refrigerant doesn't react with moisture and turn corrosive so if there's a little water in the system it's no big deal.
Technically you could reuse your dessicant cannister anyway, you'd just have to bake it in the oven for a while to boil out the moisture. My friend's air dryer setup for his air compressor for painting has you do this rather than replace the dessicant and it's a $600 unit that's supposedly pretty high end. No reason it wouldn't work provided the receiver/dryer canister is good for a half hour or so at 300+ degrees. Just look for dessicant drying instructions for some better details, I'm not positive on the temperature required offhand.
Doing the hoses sucks no doubt about it. Do all the seals/o-rings while you've got it apart and save yourself some trouble. I would definitely advise checking around for somewhere that sells A/C o-rings in bulk (most good AC compressor service places do). Seeing as you're in the Los Angeles area there's bound to be one somewhere within an hour that would stock them. (not including waiting on the LA traffic of course). The ones from Porsche are way overpriced and refrigerant o-ring is a refrigerant o-ring, the rest is just markup. Also there's some sealants for o-rings and the like for refrigerant use. Can't recall what the actual name is but just compare it to snot and they should know what you're talking about. It's pretty wierd stuff, goes on as a liquid but it's also resilient and rubbery at the same time. Supposedly seals even better than teflon tape and paste do and doesn't cause problems with refrigerants.
I think the aftermarket compressor you're thinking about is a Sanden probably, they're one of the most common for aftermarket A/C use.
My Geo Tracker (stop laughing, the little bugger is damn near bulletproof even if it is gutless and kinda silly in general) uses the exact same Nippondenso compressor except for a different pulley and the port adapter that bolts on the top. I've been running the Envirocool in that for a couple years with no issues whatsoever. It actually uses less engine power than R12 and definitely less than 134a since the hydrocarbon based refrigerant is easier to compress. For what it's worth Mitsubishi Eclipses also use this same compressor, I suspect a whole lot of stuff uses that particular Nippondenso compressor given differences between the 3 vehicles that I know for sure use it.
I promise you the Envirocool won't cause your existing compressor to fail any sooner than R12 will. If anything it's going to make it last longer. Look up the Envirocool website they've got the typical Q&A faq with all that crap answered already. This is of course assuming they're being truthful but having used the stuff myself, I think they are. One other nice thing with the HC based stuff is that you can skip the new receiver/dryer. The HC refrigerant doesn't react with moisture and turn corrosive so if there's a little water in the system it's no big deal.
Technically you could reuse your dessicant cannister anyway, you'd just have to bake it in the oven for a while to boil out the moisture. My friend's air dryer setup for his air compressor for painting has you do this rather than replace the dessicant and it's a $600 unit that's supposedly pretty high end. No reason it wouldn't work provided the receiver/dryer canister is good for a half hour or so at 300+ degrees. Just look for dessicant drying instructions for some better details, I'm not positive on the temperature required offhand.
Doing the hoses sucks no doubt about it. Do all the seals/o-rings while you've got it apart and save yourself some trouble. I would definitely advise checking around for somewhere that sells A/C o-rings in bulk (most good AC compressor service places do). Seeing as you're in the Los Angeles area there's bound to be one somewhere within an hour that would stock them. (not including waiting on the LA traffic of course). The ones from Porsche are way overpriced and refrigerant o-ring is a refrigerant o-ring, the rest is just markup. Also there's some sealants for o-rings and the like for refrigerant use. Can't recall what the actual name is but just compare it to snot and they should know what you're talking about. It's pretty wierd stuff, goes on as a liquid but it's also resilient and rubbery at the same time. Supposedly seals even better than teflon tape and paste do and doesn't cause problems with refrigerants.
I think the aftermarket compressor you're thinking about is a Sanden probably, they're one of the most common for aftermarket A/C use.
04-10-2004, 06:33 PM
#9
Three Wheelin'
04-10-2004, 09:03 PM
#10
Three Wheelin'
Here is some general information (and some of my opinions) in order to help Porshe-o-phile and others become more familiar with AC systems.
First off, let’s talk about the amount of oil to add. Oil is designed to be carried through the system with the refrigerant. One of the problems when repairing an AC system without flushing components is not knowing how much residual oil is in the system. For example, assuming your 944 has the 6E171 compressor. It’s easy to drain it of all oil (approx. 6 oz.) There is a couple of oz. in the condenser, a couple of oz. in the evaporator and about 1 oz. in the drier and maybe another 1 oz. floating through the hoses. I can check the specs on the 944 for a firmer number, but estimating about 12-13 TOTAL oz. of oil on a completely virgin system would be close. But since your system is not completely dry of oil, there is some guessing to be done. The more parts replaced, the more make-up oil is needed. MY WAG for compressor replacement would be to add 6-7 oz., if you completely drain the replacement compressor of it’s oil first. Too much oil will saturate the evaporator and lead to poor cooling; too little oil will kill the compressor. You should use ester oil which is compatible with both R12 and R134a. Don’t use PAG oil. It’s not compatible with R12 or R12 oil (which is residing throughout your system now). Oil can be added through the suction side of you compressor. Don’t use the 2oz. oil-charge through the manifold set unless you are using R-134a. The oil charge has some R134A in it and will not mix with R12. You can find R12 oil charges, but oil charge sold over the counter today will have R134 in it. Get a bottle of ester oil and pour it.
Side-note: Evacuating, vacuuming and flushing are three different things. Evacuating is the method of removing (and recovering) existing refrigerant. Vacuuming is the means to pull the system into a “negative pressure” state which removes air and boils moisture out of the system. Flushing is a method of using compressed air and a flushing agent to clean debris and oil out of a system. Neither evacuating or vacuuming removes all the oil, only flushing or replacement of certain parts does.
To build your system, you need a good compressor, a new drier an O-ring kit and a bottle of Nylog which is used on fittings and O-rings to prevent leaks. You need ester oil. You may choose R-12 or R134a, but do not use blends. Many service stations charge with “freeze 12” and other blends which are not a true R12 Freon. Bad for system!! It’s a simple choice. True R12 or R134a only.
I see that you have chosen to stay with R12 which is a good choice but I doubt seriously that any shop will charge 30 oz. of PURE R12 for $20. Make sure you know what the shop is using and don’t let them put any type of blend in the system. Nothing is “the same as R12” except pure R12.
What you can do prior to taking the car to the shop is to replace all accessible O-rings with new ones and use Nylog. You can install your compressor and drier and add the proper amount of oil to the system then close it up. You can make sure your condenser and radiator fins are clean of debris for optimum airflow through the condenser. Take the car to the shop and have them pull a vacuum on it. If the system is leaking big time, they will have a problem pulling the vacuum deep enough. If they do get the vacuum deep enough, the system should be able to hold the vacuum for at least 30 minutes. If it can’t, you have a leak.
Pulling a vacuum and knowing the system leaks may not point you to where the leak is.
Charging the system with refrigerant and dye, then running the system is an easy way to find the leak. The sucky thing about R12 is that 1) shops are not supposed to charge a leaky system with R12 and 2) R12 is much more expensive than R134a and charging the system with R12 just to find the leak can be costly. Your call, but it’s a crap-shoot. And no, you can’t charge the system with cheap R134 and dye to find the leak then switch back to a R12 charge after the leaks are fixed.
Many people overlook the importance of vacuuming down a system prior to charging. This is especially important (read: mandatory) if the system has bee opened to the outside air as when system parts are being replaced. Moisture kills A/C systems. It creates acid which eats the system from the inside out. The drier is not designed to overcome the moisture introduced by and open-to-the-outside-air system. Vacuuming removed debris and the negative pressure lowers the boiling point inside the system to a point where moisture will boil and be carried out of the system by the vacuum pump. When charging the system in this negative pressure state, you are charging INTO the vacuum, which is a good thing. If charging by 12 0z. cans, the first can will be sucked into the system even with the compressor off! When people say that they couldn’t get the specified amount of refrigerant into their system, often times it’s because they didn’t pull a vacuum and instead charged a neutral pressure system. The air in the system is taking up space needed by the refrigerant.
One more thing- If you choose R134a, charge only 80% of the listed R12 system capacity. It’s easy to over-charge with R134 and charge past the optimum point for cooling. Manifold gauges are a must. Pressure and cooling temperature are related.
One of the best sources of A/C information and discussion is the forum at
Aircondition.com forum
Good luck,
Greg
First off, let’s talk about the amount of oil to add. Oil is designed to be carried through the system with the refrigerant. One of the problems when repairing an AC system without flushing components is not knowing how much residual oil is in the system. For example, assuming your 944 has the 6E171 compressor. It’s easy to drain it of all oil (approx. 6 oz.) There is a couple of oz. in the condenser, a couple of oz. in the evaporator and about 1 oz. in the drier and maybe another 1 oz. floating through the hoses. I can check the specs on the 944 for a firmer number, but estimating about 12-13 TOTAL oz. of oil on a completely virgin system would be close. But since your system is not completely dry of oil, there is some guessing to be done. The more parts replaced, the more make-up oil is needed. MY WAG for compressor replacement would be to add 6-7 oz., if you completely drain the replacement compressor of it’s oil first. Too much oil will saturate the evaporator and lead to poor cooling; too little oil will kill the compressor. You should use ester oil which is compatible with both R12 and R134a. Don’t use PAG oil. It’s not compatible with R12 or R12 oil (which is residing throughout your system now). Oil can be added through the suction side of you compressor. Don’t use the 2oz. oil-charge through the manifold set unless you are using R-134a. The oil charge has some R134A in it and will not mix with R12. You can find R12 oil charges, but oil charge sold over the counter today will have R134 in it. Get a bottle of ester oil and pour it.
Side-note: Evacuating, vacuuming and flushing are three different things. Evacuating is the method of removing (and recovering) existing refrigerant. Vacuuming is the means to pull the system into a “negative pressure” state which removes air and boils moisture out of the system. Flushing is a method of using compressed air and a flushing agent to clean debris and oil out of a system. Neither evacuating or vacuuming removes all the oil, only flushing or replacement of certain parts does.
To build your system, you need a good compressor, a new drier an O-ring kit and a bottle of Nylog which is used on fittings and O-rings to prevent leaks. You need ester oil. You may choose R-12 or R134a, but do not use blends. Many service stations charge with “freeze 12” and other blends which are not a true R12 Freon. Bad for system!! It’s a simple choice. True R12 or R134a only.
I see that you have chosen to stay with R12 which is a good choice but I doubt seriously that any shop will charge 30 oz. of PURE R12 for $20. Make sure you know what the shop is using and don’t let them put any type of blend in the system. Nothing is “the same as R12” except pure R12.
What you can do prior to taking the car to the shop is to replace all accessible O-rings with new ones and use Nylog. You can install your compressor and drier and add the proper amount of oil to the system then close it up. You can make sure your condenser and radiator fins are clean of debris for optimum airflow through the condenser. Take the car to the shop and have them pull a vacuum on it. If the system is leaking big time, they will have a problem pulling the vacuum deep enough. If they do get the vacuum deep enough, the system should be able to hold the vacuum for at least 30 minutes. If it can’t, you have a leak.
Pulling a vacuum and knowing the system leaks may not point you to where the leak is.
Charging the system with refrigerant and dye, then running the system is an easy way to find the leak. The sucky thing about R12 is that 1) shops are not supposed to charge a leaky system with R12 and 2) R12 is much more expensive than R134a and charging the system with R12 just to find the leak can be costly. Your call, but it’s a crap-shoot. And no, you can’t charge the system with cheap R134 and dye to find the leak then switch back to a R12 charge after the leaks are fixed.
Many people overlook the importance of vacuuming down a system prior to charging. This is especially important (read: mandatory) if the system has bee opened to the outside air as when system parts are being replaced. Moisture kills A/C systems. It creates acid which eats the system from the inside out. The drier is not designed to overcome the moisture introduced by and open-to-the-outside-air system. Vacuuming removed debris and the negative pressure lowers the boiling point inside the system to a point where moisture will boil and be carried out of the system by the vacuum pump. When charging the system in this negative pressure state, you are charging INTO the vacuum, which is a good thing. If charging by 12 0z. cans, the first can will be sucked into the system even with the compressor off! When people say that they couldn’t get the specified amount of refrigerant into their system, often times it’s because they didn’t pull a vacuum and instead charged a neutral pressure system. The air in the system is taking up space needed by the refrigerant.
One more thing- If you choose R134a, charge only 80% of the listed R12 system capacity. It’s easy to over-charge with R134 and charge past the optimum point for cooling. Manifold gauges are a must. Pressure and cooling temperature are related.
One of the best sources of A/C information and discussion is the forum at
Aircondition.com forum
Good luck,
Greg
04-10-2004, 09:25 PM
#11
Three Wheelin'
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Greg,
Can you confirm that the proper place to charge the early AC systems is through the port on top of the compressor. There is also a port on the drier, but I think this is on the high pressure side, right?
Also, any suggestions for attaching a hose to the compressor? I had planned to get an "L" shaped schraeder adapter and putting a R134a adapter on that.
Can you confirm that the proper place to charge the early AC systems is through the port on top of the compressor. There is also a port on the drier, but I think this is on the high pressure side, right?
Also, any suggestions for attaching a hose to the compressor? I had planned to get an "L" shaped schraeder adapter and putting a R134a adapter on that.
04-10-2004, 11:06 PM
#12
Three Wheelin'
Can you confirm that the proper place to charge the early AC systems is through the port on top of the compressor. There is also a port on the drier, but I think this is on the high pressure side, right?
I can get my R12 charging hose on my 924S (early 944) compressor, but it's a tight fit. The anti-blow-back fittings on some charging hoses are huge in diameter and may not fit. There are some pretty small R12 hose fittings that will work.
Also, any suggestions for attaching a hose to the compressor? I had planned to get an "L" shaped schraeder adapter and putting a R134a adapter on that.
On my 928, there is a tight spot on the L/P connector also. I took a charging hose and ground down the knurrled part of the fitting which made it smaller in diameter and it fits the 928 great. This idea may work on the 944 as well
04-11-2004, 12:40 AM
#13
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Thanks for the info, Greg. The fitting on my '83 is so close to a bracket, that the R12 hose I have won't fit. The ferrule on the hose is long and it just won't bend enough to fit it in. I manage to charge most some through the HP port, but I'm out of R12. When it leaks out, I'll convert to R134a.
04-11-2004, 10:22 AM
#14
Three Wheelin'
83na944,
If you decide to use a right-angle type adapter and it has a shrader valve, remove the shrader valve from the compressor fitting when installing the right angle adapter. Otherwise, there may be no flow through the adapter.
BTW, charging through the high side with the compressor running is not recommended and can be very dangerous. The high side pressure can be 250+ PSI and 1) the freon can't flow into the system against that much pressure and 2) the high pressure going to the can can make the can explode! It has happened to many people trying to charge using the high side while operating the compressor.
Greg
If you decide to use a right-angle type adapter and it has a shrader valve, remove the shrader valve from the compressor fitting when installing the right angle adapter. Otherwise, there may be no flow through the adapter.
BTW, charging through the high side with the compressor running is not recommended and can be very dangerous. The high side pressure can be 250+ PSI and 1) the freon can't flow into the system against that much pressure and 2) the high pressure going to the can can make the can explode! It has happened to many people trying to charge using the high side while operating the compressor.
Greg
04-11-2004, 12:45 PM
#15
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I just finished retrofitting my 86na with r134. The 86 is nice in that you have a high and low fitting on the top side. I am anxious to see how long this nippondenzo last, probably not long with whatever you put in it. I just bought the car in Oct 2003 and was surprised that the compressor was good. This is my 4th 944 over a period of years and the Nippondenzos are not good compressors. I remember on a previous 86 i put 3 Nippo's on it and my 88 after the 2nd Nippo I put a Sanden on it. The thing I like about R134 is that if I get a little low on freon then I can run into a parts store and buy a can an put in. So far it is cooling great, if the Nippondenzo goes bad I will put a Sanden or Kuehl on it not another Nippoondezo.