Latest dope on R12 to R134 conversions - experience?

Hi, I started this thread with the question and here are some updates:

I have license for R12 if I want to buy it but I first changed over a 1990
Mercury Topaz of a senior citizen from R12 to R134.
The kit cost 32 dollars and has leak sealant and O ring conditioner and uses
ester oil.

The air on it was excellent and cold. OK perhaps not quite as cold as full
charge of R12 but cold enough that you had to turn the air down after a
couple of minutes in 90 degree temperatures.

I then did my GolfGL88 that was 10 times faster as I had to take some parts
off in the Mercury to get to the low pressure port. The Golf gobbled up 2
cans in minutes and I was surprised how fast. I put in a few ounces of a
third can.

The first thing I noticed with the Golf was that the pressure was higher
running around 280 to 300 psi and I was getting a bit paranoid or burst in
an older system. It did not get higher than 300 psi. I looked this up on
Google and found on remark that made sense that AT IDLE the pressure of R134
is higher because the fan is not as effective as cooling the liquid
refrigerant as cooling R12 but going down the road the condenser brings down
the pressure. Also stated in VERY long bumper to bumper traffic it might be
straining the system if at a stop for a very long time with R134 in an R12
system and may pay to turn the system on and off.

The Golf is VERY cold with the R134. What all did I do? Just like the
manufacturer said. I used a vacuum pump (they don't tell you this when you
buy the self retrofit kit on the box but tell you on the website) to remove
ALL the R12 that was left in the system (yeah I know it should have been
captured but get real a ton of people may let out a small amount of R12 on a
system needing charge - I don't condone it)

I held a vacuum for about 20 minutes. I simple used one of those (I think 20
buck on Harbor Freight) device that you hook your compressor to and without
moving parts it pulls a vacuum. It works good I even used it with a house
system (pump).
After I pulled a vacuum with both cars I changed to the R134 port and
connected and let the R134 in.

Nothing else was done BUT there is a lot of misinformation out there,
depending on opinion. Even though the manufacturer's website says all you
need is to pull a vacuum. R12 and R134 mixing is suppose to create some form
of acid, auto parts workers will tell you all kinds of different things if
you try to get some input. The store I bought the R134 kis, Advanced Auto,
told me I had to change the receiver dryer and remove the oil from the
compressor, THEN told me it had to have PAG oil put in. This is the
*classic* retrofit along with flushing and perhaps changing an orifice if
provided for the car BUT I did none of this.

Just pulled a vacuum. Put the R134 exactly as per manufacturer's instruction
on their website and it was uneventful. I am VERY satisfied with it. One
note: on their FAQ on their website in a sentence it talks about a 29 inch
vacuum as "water" isn't that 29 inches of mercury?

Would not hesitate to do it again. VERY easy and the next time I need to top
it up, not 30 dollars for a 12oz can of R12. More like 8 or 9 dollars a can.
Here is the FAQ page from the manufacturer for retrofitting for the product
I used that cost 32 bucks with everything. (except the ability to pull a
vacuum for someone else without a vacuum pump)
http://www.id-usa.com/how_to_faqs_retrofitting.asp

My suspicion is that it could work probably very well even without pulling a
vacuum but not a good idea if you can do it.

Harry