STLRJ

Where did you get the plumbing connections to go from the Coleman propane bottle to the R12 Schraeder-type valve on the A/C system?

I *think* SteveW here on the board has mastered the "cocktail" of propane and isobutane. He's also figured out the plumbing necessary for the installation.

Cool! Someone please post the details. My C2 needs a recharge, and if I can improve the efficiency, I'm all for it.

Hi guys. Yes I did master the installation of isobutane and propane a couple of years ago in the installation of an AC system in my Toyota pickup and it's still going strong and freezing my nuts off. It was based on the faqs on the ACVette page. I still have a couple of cans of R12 I smuggled in from Mexico a few years back, and will be installing the propane mix in my Carrera when I run out. Basically in order to create the mix you need propane and isobutane. For propane, you want the dry type, and that would be the torch propane you can pick up at Home Depot for about $2. Isobutane is a little trickier and is not the same as regular butane. What I finally found was MSR camping fuel at Sport Chalet, a local sporting goods chain here in California. MSR camping fuel is a mix of 80% isobutane and 20% propane. The great thing about the MSR can is that it has the can top which is similar to the top of an R12 can, which allowed me to use my old R12 can adapter and hose fitting right off the can.

http://forums.pelicanparts.com/uploa...1067223288.jpg

You want to use about 80% propane, and 20% isobutane added to the mix to emulate pressures closer to R12. I don't think exact mixtures really matter. BTW, back in the day, before R12, propane was the common refrigerant gas used in all refrigeration systems in buildings etc, or so I read. You will use much less of this gas by weight than R12. I don't remember all the specs, but off the top of my head, a 911 uses about 36oz of R12, so you would use about 14 oz of this propane/isobutane instead. Don't put in 36 oz of gas, as I learned or it will overpressurize the whole system. You can premix everything in a old container, but I did it the lazy way and injected them separately. Since all the gasses are hydrocarbons, everything, including the seals, hoses, and compressor oils and gasses are fully compatible, and nothing has to be changed.

Here's a copy of an email I wrote to Tim Polzin a while back, so which details more about what I did:



First read this faq:
http://www.vettenet.org/acfaq.txt

Most of my time was spent trying to figure out how fabricate the adapters to inject the gasses
into the ac system.

Get the isobutane (not regular butane) from a camping supply store. MSR(Mountain Saftey Research) makes
a 8 oz stove fuel consisting of 80% isobutane and 20% propane, about $4.00. Use a standard AC hose
adapter on the can top to attach a standard R12 manifold hose to the top of the can, and attach
the hose to the car's ac system.
http://www.msrcorp.com/stoves/fuel_blend.asp

Get the propane from a standard propane torch kit. Here in the U.S. I picked up a 14 oz. Bernzomatic
www.bernzomatic.com kit from Home Depot for $12.00.


2 Pc. Pencil Flame Torch Kit
Kit includes torch unit and 14.1 oz. propane cylinder.

http://forums.pelicanparts.com/uploa...1067224209.jpg

Unscrew off the tubelike torch tip, you dont need it. Rethread the remaining tip (penislike tip) with a thread die
matching the threads of a standard manifold hose adapter. I forget what it is, but I think its something
like 7/16x20, or 1/2x20, or 3/8x 20. That way you can screw one end of an ac hose to the torch tip, and the
other end to your ac system. Then take a small drill and drill through the penislike tip all the way through the checkvalve
at the tip. The current hole is very tiny, like a pinhole. There is another checkvalve at the underside of the
torch unit that should be drilled out. Unscrew and remove the part there with a 8mm socket, and drill out
this little part from the inside. Don't drill the all the way through, to the other side, because you will see that
the little part has to have its exterior hole small enough to push the pintile valve on the propane cylinder.
Remove all the little parts and spring inside. You are done. Screwing on a manifold hose to the rethreaded
torch end, the torch unit now acts as valve adapter for
you to inject the propane into the car. You probably want to aim for the ideal of 21% isobutane, 79% propane,
but it doesnt matter too much. It has worked for me with 100% propane too. Isobutane acts to lower overall
system pressure a bit to match R12 more, and also to dissolve and circulate the mineral oil in the system.
It's supposed to be more efficient on your AC system than R12 because it requires less compressor pressure
to acomplish the same heat removal. You are supposed to inject half the equavilent weight of propane/isobutane
into your system as compared to the weight of R12. The gasses are compatible with all the oil and seals in a R12
system, so there are no upgrades/changes to perform.

It's a little hard describing, but I hope I was able to make it understandable. Any questions?

Hugh, I found the adapter for the Colman bottle at Marin Outdoors, but any camping supply store should have it. The adapter I have has a shut off valve incorprated in its design which is what you will need.

Joe