I am so glad this issue is being covered. Good article, but there are a few things I would like to offer. First, when refurbishing an old system, flushing is not needed unless the original system was damaged by a compressor blowout. This can be confirmed by inspecting the orifice or control valve and looking for foreign matter, which is likely from bits of the trashed compressor. In this case, all components must be flushed and blown out with compressed air. Second, flare fittings are fine, but the hoses must be replaced. To do this, fittings with matching configuration can be sourced (angle, size and gender) that are designed for use on R134a compatible hose. You also must replace your clamps with ones designed for R134a. The original clamps, which look like those used on radiators, are not strong enough to seal. You used to have no choice but to go with crimped ends, which required expertise and tools beyond the reach of DIYer's, but now there are systems that use bands attached with inexpensive hand tools. The other issue I would like to address is the retrofitting of R134a into existing systems. You must remove all R12 from the system, but the R12 oil is not an issue if you do not use PAG, but instead use ester oil. I still recommend replacing the receiver-dryer, because this does remove most of the old oil and you get a fresh start with the all-important dryer dessicant.
I would also say that when adding the ester oil, only use enough to replace what is normally lost in a component replacement. For instance, receiver-dryers retain some oil so only add what is needed for that component.
My 85 Pontiac still has the original R12 from the factory. I never seen a system last so long. I already have R12 to go back in if the seal leaks.
The R12 gets to nearly 40 degrees at the vent. It is just a better product.
I also work for a intake Air Dealer. I can say they are a top notch mfg and product. I work directly with them to set up AC units and they have been great. Yes once in a while there are issues as most systems are custom and I never had an issue unresolved.
I have to get these right as I sell these globally and can not afford issues in Perth, Tokyo or in the Middle East.
Often service is best working with a retailer as that is their job retail. Dealing direct with mfgs can vary as they are not retailers. If you don’t know who to call it can be challenging.
Something that anybody who plans to recharge their A/C for ANY reason should know is to STAY AWAY from the crappy refrigerant that so many auto parts stores sell. What I mean is any refrigerant that contains stuff in it that is so-called "stop leak" is extremely BAD. The stop leak may seal leaks, but it also plugs up the condenser passages, the TXV or orifice tube, and certainly doesn't do anything else any good. It can also ruin recycling machines, to the point that its cheaper to buy a new one, than fix the old one. There are kits out to determine if a system has stop leak in it, but the ones I've used were of questionable value. A decent A/C shop should also have a refrigerant identifier machine, which can tell you if you have some weird stuff in there, along with air and hydrocarbons. Hydrocarbons usually come from using crappy R12 replacement refrigerants that use a propane base. While propane (R744) makes an excellent refrigerant, it has this nasty tendency of exploding or catching on fire, and is NOT legal for automotive use. Just buy pure R134a with no sealant, no dye, no nothing! Maybe dye is OK, but you only need a few ounces. Several cans of 134a with dye is gonna be too much for most systems.
While I'm on my soapbox, I would advise to stay away from those cheapo "suicide kits" sold alongside that crappy refrigerant. A set of Harbor Fright gauges would be a good investment instead. Can taps can be purchased at A/C supply houses, and probably NAPA (not a sponsor). OK, I'll shut up now.