[Matt88S]

There are quite a few substitutes out there. The problem isn't that they don't work, its that most of them are flammable. HC-12a is flammable and therefore is not an Acceptable Substitute according to the EPA’s SNAP program. Incidentally, HC-12a is a identical blend to Duracool 12a, also not considered acceptable for the same reasons, it’s flammable.

Have you thought of using Freeze 12? Its an Acceptable Substitute according to the EPA’s SNAP program and is not flammable. It is also fairly reasonably priced, about $7-$8 a can, only a couple dollars more than R-134a. I recharged my 88 S with it and it worked very well, this was in Oklahoma summer heat around 90-100F. It would chill the car until you had to turn it down or freeze, Saab A/C systems seem to work very well with the appropriate refrigerant in them.

Unfortunately it has a slow leak in the system and about a month later it had all leaked out. I never got around to rebuilding the A/C system, but now as the heat is building back up to the 80's and 90's I am thinking I had better get it going before the heat really hits. If I have some new hoses made, replace the O-rings, and recharge it, and I should be good for several years at least.

 

[Matt88S]

Its just another R-12 substitute. It suposedly works almost as well as R-12 did and is compatable with R-12 mineral oils and whatnot so you can just add it without flushing out the system like when you change to R-134a. It also operates at pressures similar to R-12, R-134a operates at higher pressures than either one. Freeze 12 is not flammable so the EPA deemed it "aceptable". Whatever that means.
You used to not have to have a license to buy it but now that it seems to be gaining recognition I noticed the local parts stores are requiring you to have a license. I don't know what its like in your area, I think you can still get it online without a license, I don't know though, I've never tried, plus I have a license so I don't have to worry about that anyway. :roll:

Here's a couple links to what the EPA considers "acceptable" and "not acceptable".
http://www.epa.gov/Ozone/snap/refrigerants/lists/unaccept.html
http://www.epa.gov/Ozone/snap/refrigerants/lists/mvacs.html

We need cdaly's opinion, he used to be in the transport refrigeration field and knows a lot about A/C systems and refrigerants.