Jim Devine

Dallas Craigslist- Search under "for sale" & put in "R12"
or if wanted "R134" in the search box. Some days nothing turns up,
just take a quick look once in a while.

http://dallas.craigslist.org/dal/pts/3849911673.html

FredR

Oh yummy- I missed the start of this!

As you can imagine with temps in 44c range at the moment a/c is rather critical and the 928 can struggle even when perfect. Until recently R12 was available here [from India] but now ti has more or less dried up- maybe less of a problem for the chaps in Dubai.

I changed my hoses, I changed the compressor body and dynamic seals, I was advised the GTS ring seals are just fine but remain a bit supsicious as my variant [registered August 92] had the R12 system fitted. Today's compressor oils are compatible for both R12 and R134 so that is not an issue.

I find that R12 could cool the cabin well on very hot days here [at speed] and R134 by comparison struggles but can be considered acceptable when optimal. I do have a fugitive leak somewhere- we cannot trace where it is despite using dye tracer/UV light to find it so fear the problem could be in the evaporator [hopefully not]. I can get by for about 3 months before needing to plop a bit more gas in- seems a soft option to me.

The 134 is a bit more prone to leaking presumably because of the slightly higher operating pressures so I guess I just have to live with it for the time being.

The best refrigerant is propane- it'll freeze you stupid until the halon system you fitted with auto flame detection kicks in [LOL]! It has been done and the GT it was fitted to was well and truly toasted so do not try this at home!

Regards

Fred

WallyP

"Today's compressor oils are compatible for both R-12 and R-134a so that is not an issue."

Well, POE is acceptable for both, but...

R-12 - Mineral oil is best, and should be used for all R-12 installations.
R-134a Factory installation - PAG is best, and is normal factory fill. This should be used when servicing an original R-134a system.
R-134a Conversions - POE is acceptable for both R-12 and R-134a installations, and should be used for any R-12 to R134a conversation where the system will contain residues of mineral oil.

An automotive system depends upon the oil being circulated with the refrigerant.
R-12 will carry mineral oil very well, but R-134a does very poorly at carrying mineral oil.
R-134a carries PAG very well. PAG does not play well with mineral oil, and is not recommended for any system that contains residues of mineral oil.
R-134a carries POE well, and POE does well with mineral oil.

Bottom line: Use POE in any system converted from R-12, and use PAG in any system that was R-134a from the factory.

When R-134a was first used in factory installations, tests showed that the smaller molecules of R-134a would migrate thru the walls of the hoses used for R-12 quickly enough to be a problem, so "barrier" hoses were developed for the factory systems. At that time, it was recommended that the R-12 hoses be changed to the newer barrier hoses during a conversion. Later studies of conversions revealed that hose leakage was much less of a problem than expected, primarily because the oil in the system filled the pores in the hoses. Most conversions are now done without changing the hoses (unless they are bad, of course).

davek9

Is it still recommended to install a relay to run the aux fan whenever the AC is on and not rely on the dryer temperature switch when converting to R134a?

Great info on the oil, auto parts store told me to use PAG per their book

Thank you,

Dave

dprantl

+1. Never use PAG oil in a system that has ever had R12 mineral oil in it. If someone tells you that PAG is okay in such a system, run away.

Dan
'91 928GT S/C 475hp.460lb.ft

The Forgotten On

What if you are literally changing everything in the system to work with R134a like I am. that includes changing put the compressor, lines, o-rings etc. Should I convert the system to PAG oil or still use POE?

dprantl

If you are replacing *every single* component with new, then maybe, but I doubt you are. For example, are you getting a new fuel cooler or evaporator? Flushing components can still leave traces of mineral oil in the system and ester oil has been proven to work well with R134a, so there really isn't any reason to try and safely put PAG in there.

With regards to hoses, the hoses on later 928's seem very robust compared to the hoses in other cars of the same era and have been working fine with R134a in my car so far.

Dan
'91 928GT S/C 475hp.460lb.ft

The Forgotten On

dprantl, I am replacing everything except the evaporator which I will have flushed. MY is 1981 so no external coolers to worry about. The system I am guessing hasn't worked in the last 20 years so there will be very minute traces of mineral oil. If I find out my evaporator is leaking that will be replaced also so it should be safe to add PAG. I am also using a griffiths kit.

WallyP

Your car, your choice - but two questions...

Are you replacing all the hard lines, including those where the engine has to be pulled to replace?

Why the urgency to use PAG when POE works well?

Ad0911

OK, perhaps DuPonts R437a than. I hear you don't have to replace the seals and you can use the mineral oil like what you use when having R12

dprantl

R437a is a refrigerant blend that is almost 80% R134a. The rest is R125 with a little bit of butane sprinkled in. If you spring a leak with that, you have no idea how much of each fraction leaks out, and it could be the fraction whose sole purpose is to carry around the mineral oil. May as well just switch to ester oil and use straight R134a because performance-wise, it's probably the same. It really is not that difficult to flush the components and put in ester oil.

Dan
'91 928GT S/C 475hp/460lb.ft

dr bob

What Dan said, plus...

A typical reason for considering a refrigerant change is that your old refrigerant has leaked out and you want something to put in. Regardless of the refrigerant you plan to use, you really want to solve the leakage issue first. Pre-'93 US cars and some '93 cars came with R-12, and seals that get tired with age. So at minimum, any refill must include new o-rings at every junction/connection. The effort is the sameto put in the newer o-rings that work with R-134a, and since it's all going to be apart it's not a problem draining the oil from each component and refilling with POE for compatibility with R-134a and backwards compatibility with any residue of mineral oil you didn't flush out. Rebuild the hoses from the compressor with barrier style flex sections. New R-134a-compatible drier, required since you have the system open to atmosphere.

Now, which refrigerant to use. R-134a or a blend that's predominantly R-134a. Tough choice...

The Forgotten On

I will use dprantl recommendation to use POE instead of PAG oil. I was wondering if I should have my lines rebuilt with as barrier lines or keep them stock because I know the old lines leak R134a like a sieve because of the smaller molecule size. And fortunately there are no hard lines in the engine bay. No fuel coolers either so there is just generally less to worry about.

curtisr

It makes me laugh when I read that 12a is NOT available south of the 49th parallel--it's manufactured in the US!

Anyways, 12a (RedTek) is half-price starting tomorrow at Canadian Tire stores. While I suspect the DuraCool brand is made in the same factory (haven't checked and don't care) as RedTek, you can find this slightly cheaper alternative at Princess Auto stores here in the Great White North.

whatudrivin

Is it illegal to import the 12a from Canada to the US?