I tried a charge with Dura-Cool. I am not getting much cooling at all
from the A/C. None before  (there was a leak on the condenser), and
little after.  There is enough that at night when the outside temp is
in the 80s you are cool, but it is overwhelmed by humid mid-90s
weather in the daytime.   I didn't replace the accumulator before
recharging. ALso I was told that the orifice tube might be clogged up.
So I have an accumulator ordered (along with the AMM) and also a new
orifice tube. Will pump it down again and refill with R-134 this time.

ANother problem with the A/C is that the blower puts out a puny volume
of air. I know it is rotating freely.  I know it is controlled somehow
by computer, because every time you go up even a slight uphill grade
(or accelerate), the blower cuts back and there is practically no air
blowing out the vents. Also the compressor is cut off under load.  I
would really like to try disabling this feature and see if car still
performs OK, because it makes it get even hotter. I ckecked the
voltage to it when it is going "full blast" and it is getting about
the full system voltage.....maybe it just doesn't blow nearly the
volume of air that a modern sedan does.   But I don't know, since I
don't have another 740 to compare with.  Could I get some other more
powerful motor for more air volume?
 How can I check to see of there is some restriction of the air inlet
to the blower? I think there is a vacuum operated door, but maybe it
is a hot/cold blend door on the outlet side of the blower.
   ALso, I need to know where the orifice tube is installed....I
don't have a clue where to find it.    
    Its probably not the fault of the Dura-Cool, but there is some
other issue with it.

Thanks, Geronimo