If you have a 1970 Buick and you want to update the A/C system, what is involved? Is it just changing to the new refrigerant? Or, are there new parts to changed also?
You need to flush the old system out with AC flush, change to the green o-rings, have the POA Valve recalibrated for 134, pull a vacuum, install 134.
If you want to go "all the way" you should have the hoses replaced with the barrier style in addition to the items mentioned above.
Actually, concerns about excessive ambient leakage through non-barrier hoses have proven to be a non-issue in the years since the change to R134a. There is some, but as it turns out, no more than with R12. All new vehicles are mandated to have barrier hose to reduce even that tiny amount of leakage. The main reason to replace the hoses today is the fact that they're 40 years old. It certainly is a good idea, just not for the reason many folks think. Same thing with the o-rings in all of the connections. The new seals work better regardless of refrigerant. Estimating the cost is much like estimating paint or an engine overhaul. The price can vary widely depending on what is found when you open the system and inspect it. DIY, I always recommend you budget $500 to do it thoroughly and correctly, then be pleasantly surprised when it is less. Add about $200-250 to have it done in a shop.
