You are totally correct, but the problem is that R12 is now illegal to use so that is why took the cheap option put R134a in. The poor old ED had a A/C system specifically designed for R12 which from what I have read has different properties to that of R134a and hence how it performs poorly if you replace one gas with another. I have read about other refrigerants (
http://hychill.com.au/products/minus-30) that have similar characteristics as R12 but I would like to hear from others with ex R12 setups and what they did to overcome the poor performance with R134a. I found this article regarding R12 over R134a in a R12 setup....." There is no question that R12 performs better than R134a, but by how much? According to statistics, for an R134a system to have comparable performance to R12, the condenser must be increased by 30%. That is a huge feat. I am not whether that correlates which stating that it performs 30% worse when in the same systems, but one can make a pretty good judgement that if it requires 30% greater surface area to meet prior performance, it is safe to say R12 or CFC-12 is far superior. "