Scruit

If you need to crack open your A/C for repairs or parts replacement, then you need to recover the refrigerant first. You should never vent R134a into the atmosphere or the EPA and the Tree Huggers will kick the crap out of you.

I know that new R134a is about $9 for 12 oz (at the time of writing, may go up), and our cars prolly take about 2lbs, so that's about $27 for a full charge.. It's probably not cost effective in terms of saving you the cost of refrigerant. BUT also remember that venting is illegal ($25k fine if that neighbor you pissed off last week sees you doing it and rats you out) so you should recover anyways, even if you're just going to recycle the old stuff. If you have R12 then you're on your own, as it's illegal for DIY stuff. R134a is ok for DIY.

So you've decided to recover the refrigerant, but you don't want to spen $700 on a recovery system or $150 on having the local shop do it...

You will need: (I had all this lying around 'sept the dry ice so it cost me $3 total)

- Interdynamics R134a charging hose, with guage is ideal (or manifold guage set, if you have one like me)
- 3 empty R134a cans with Can Taps
- 2lbs dry ice (try your local Graeter's Ice Cream)
- Couple bottles of 91% ispropyl alcohol
- Styrofoam cooler
- Leather welding gloves and safety glasses
- Food scale

Preparation:
- Break up the dry ice into small pieces in the cooler
- Add the ispropyl alcohol
- Weigh the empty R134a can with cap tap attached to get the empty weight

First Can:
- Screw the can tap on the first R134a can, close the valve, and hold it in the dry ice bath for a couple minutes
- Hook up the charging hose (or gauge manifold) and open the can tap
- Listen for the sound of it filling, and keep sloshing the dry ice bath to keep the can cool. I arranged the dry ice so it covered the whole can
- After a few minutes close the can tap and disconnect the charging hose
- Weigh the can. You need to make sure you don't exceed the liquid capacity of the R134a can, usually 12oz
- When it's full remove it from the bath and diconnect the chargin hose from the can tap. With the top up, crack open the valve for a second to purge the air.
- Leave the can tap in place and set the can aside for recycling or re-use.


- Repeat with 2nd and 3rd cans, until nothing else comes out, or guage reads basically zero.

- You can now take the refrigerant for recycling, set it aside for later use etc or whatever, just don't vent it.


You can use a version of this tecnique for consolidating multiple half-cans of 134a - just drop the can you want to fill into a dry ice bath and put the other can in warm water - the 134 will flow from the warm can to the cold can. This works because the lowe temp refrigerant is at a lower pressure. Refrigerant MUST be at a predictable pressure for any given temperature, so by cooling it to -100 (dry ice) you force it to be at a pressure which is less than atmospheric pressure - it will therefore draw the refrigerant into the can.