134a conversion, High and Low pressure readings

[Huppert, Eric]

Gentlemen,

Difficult patient: 90 Audi 200TQ

After numerous issues with the AC system I'm getting fairly close to cold
air, versus cooler air!

Of course I only have R12 gauges, and have had fairly little luck finding a
134 pressure chart similar to the R12 charts which were relatively common
back when I was turning a wrench for a living. And my vacuum pump will only
pull about 28", which I know isn't really enough...

System calls for 1000 grams R12. All the info I've found on 12 to 134
conversion states start with 70-80% 134. Charged with two cans, apx 680g and
high side is over 250lbs (above idle) Ambient temperature was apx 85F...
Press seems high? Vent temp was around 50F.... As for low pressure, need to
get 134 adapter to hook up to low port!   

Thoughts, guesstimates on apx hi/low pressure figures????

Thanks, Eric