Dave,

I offer my comments with all due respect. Please don't take offense if I sound sarcastic or anything.

To begin with Stu Ritter does not live in the DFW area where we have an annual heat wave that lasts four months.

You can use a parallel flow condensor and still use R12, it will be all the better.

You are looking at putting some major bucks into this project for obvious and justifiable reasons. Given the overall cost of R12 would represent less than 10% of the overall project cost.

In fact to help you save some money and basically "pay" for the R12 I will loan you my vacuum pump. I am moving toward recovery/recycle machines for my vac pump function and can let my vac pump out of the shop for a week or two when you get to that stage of the project. If you would be charging from a bulk can I would also loan you a "dial a charge" which some folks prefer in place of a scale.

I have converted several 123's with reasonable results, but those results were marginally acceptable because my family and I live 20 miles out of town and do stoplight to stoplight driving VERY rarely. In the DFW area in town driving is almost impossible to avoid.

That said, I have reverse converted one of them.

Other problems with 134 conversion is getting the oil right, and the pressures for that matter. The chance of long term system survival statistically goes down in a converted system. The sightglass becomes close to useless in a converted system, and it usually takes experimentation to get the charge right, even if you carefully meter in what you think is the right amount of 134, you will most likely have to experiment a little by monitoring high side pressure. Once you achieve the right charge, there is no good way to duplicate that volume next time because you don't know exactly what it is. That means experimenting again if you have to charge again later.

An additional comment is to buy a NEW R4. I've been there, done that with rebuilt R4's. If you insist on a rebuilt, do some research and buy one from ackits or somewhere, definitely not a chain store unit.

Best of luck with your project regardless of refrigerant choice and let me know if you want to borrow my pump and dial a charge.

Have a great day,