A/C system pressure/capacity

[bosango]

Hi All,

 

Does anyone know the the system refrigerant capacity or pressure for the air conditioning unit on a 1993 Legacy LS? I'm converting to Enviro-Safe and need to recharge the system (it's been completely discharged at an approved facility - $25, no wonder folks are tempted to vent it into the atmosphere). I've heard that in general 50-55 psi should be O.K., but I want to double check that to make sure there isn't anything special about the Subie system. Thanks!

[idosubaru]

two cans should do it. LOL.

[Rooster2]

Since R-12 was declared environmentally unsafe, I have to think the switch to R-134a must be good for the environment. I would be concerned about adding something else to a system designed for 134a.

[Scoobywagon]

The early legacy's call for 2 lbs of R12. you'll need a conversion chart to determine how much of your new refrigerant you'll need.

 

As for the "safety" of 134a...well.... R134a is flammable and, when burned, becomes a neurotoxin. It is not environmentally friendly. Not even kinda. Oddly, some of the best, most eco-friendly refrigerants are not legal for use in the US.

[Legacy777]

When converting the first gen legacies to r134a, I usually recommend replacing the receiver drier with a new one, changing the oil to at the minimum esther based, but PAG is better, and charging the system to about 75-80% of its original capacity. The system refrigerant capacity will be listed on a sticker on the radiator core support.

 

Take a look at my post over the Legacycentral BBS. I go into more detail there. The only thing I would suggest changing is the use of PAG oil over esther oil. That's one I have learned after doing a couple of these.

 

http://bbs.legacycentral.org/viewtopic.php?f=11&t=1083

[bosango]

Thanks 777 - excellent post! That's just the info I was looking for. Now step aside, I'm going to get me some air-conditioned comfort.

[Legacy777]

If you have any issues or questions, just let me know.

[bosango]

Well, I had wanted to take it all to bits and clean everything out as long as it was discharged. But an unexpected time constrained, paired with the stifling New Mexico heat, forced me to get it back together ASAP.

 

The A/C system was discharged because I pulled the engine for new rings, bearings, and all that other stuff. The engine rebuild went nicely except for that friggin' lower left engine mounting stud in front of the halfshaft - damn! The A/C was working fine before the discharge and in retrospect I think I might have been able to move it all out of the way without having to take it to a shop to recover the freon.

 

Anyway, I got the Enviro-Safe kit with the gauge, borrowed a vacuum pump, sucked out all the air and moisture, and put in about two cans of the refrigerant. They claim their stuff is compatible with everything, so I didn't change or add any oil, O-rings, dryer, etc. I did have to file down the valve stem from their adapter to get the coupling to work properly. Result: the low side pressure is about 40 psi, it's COLD, and everything seems to be happy. I figure if something does clog up or poop out, at least now I can service it all at home (following the great instructions in the link above).

[Allpar Mod]

Make sure you get a pressure gauge to measure the pressure so you do not overcharge the system. 40 psi is about correct. They make inexpensive gauges that are available at most auto parts stores. Don't guess. Undercharging will result in ineffective cooling. Overcharging will damage the seals.