refilling a large r134a self-sealing can?

[csrf]

ok, i know this is going to sound crazy, and I'll probably get scolded for it, but I'll ask anyway...

A friend of mine gave me a large 35oz (1kg) can of r134a that he had left over from when he did his AC. I'm not sure where he got it (it's autozone 'shop pros' brand). It's a self-sealing can that's functional but is basically empty. I asked him where he got it and/or if he could get me another one, but he said he couldn't.

Anyway, this size can would be perfect for me to use to do the A/C on my truck (22oz), and it would avoid me having to deal with using two 12oz cans & having to purge the lines when swapping, keep track of exactly how much refrigerant I put in from each can, etc.

So, my question is 'can I transfer the contents of two 12oz cans into the larger one, by using a charging hose, a couple of can taps & ball valves?'

I was thinking I could first pull vacuum on the empty can, and then transfer over the contents of the smaller cans into the bigger can, using some warm water (or some other light heat source) to heat the smaller can & help the refrigerant expand into the larger one (and, also, by cooling the larger can in ice water?). Since the big can is designed to hold 35oz, and I'd only be putting in 22oz, I figured it would be feasible to get done without having to use much pressure & be within safe limits of the can's capacity.

Yes, I know this might be a crazy 'do at my own risk' type of activity, but I was wondering if the idea makes sense in theory, and/or if anyone else has done something like this before?

please help, thanks

[andrew vanis]

it would avoid me having to deal with using two 12oz cans & having to purge the lines when swapping, keep track of exactly how much refrigerant I put in from each can, etc.

Some thoughts -

1) seems like you'll be having to do some version of the "keep track of exactly how much refrigerant I put in from each can, etc" when you fill the larger can anyway so maybe just do that step filling the vehicle

2) some can taps (or manifolds or manifold hoses and possibly cans) have a check valve which prevent back flow which can be a:

2a) downside - it can prevent refilling the large can

2b) upside - that can prevent loss in the fill line so swapping in a second can may be a non-issue and easier by purging at the can connection - again, you'd have to do this in the fill procedure anyway.

With a stop point at the end of a full can you already have it really easy.

I discovered the check valve issue seeing if I could recapture a system for a repair into empty 12oz cans.

I'll be interested how this goes for you if you do it.

There might also be rules preventing diy recapture from a vehicle but in your case it's a transfer separate from a vehicle so not sure what rules may apply.

I could see the value in having a specific fill level can for say - going over to a friends to fill a system where a scale isn't available. In your case, finishing at the end of a can, you already have that set up from the store cans.

[Cusser]

ok, i know this is going to sound crazy, and I'll probably get scolded for it, but I'll ask anyway...

Anyway, this size can would be perfect for me to use to do the A/C on my truck (22oz), and it would avoid me having to deal with using two 12oz cans & having to purge the lines when swapping, keep track of exactly how much refrigerant I put in from each can, etc.

I think this would be way more trouble than it's worth, especially if you have a 22 oz. fill.

How often would you ever need to fill up completely? Once every 6 years? And two cans is just right for your fill.

[JohnHere]

Taking the discussion further, why not just purchase a 30-pound cylinder and be done with it? I know R-134a is more costly nowadays, but the upside is you'll have plenty of refrigerant to use in the future should you need it...and you probably will.

Also invest in a good refrigerant scale so that you can weigh-in the exact charge, which certainly is preferable to blindly "topping up" a system. ACKITS.com has them.