see post #4

with the compressor running what are the pressures on the blue gauge? both manifold valves closed.
the first can sucked in due to the system being evacuated. the second can will not suck in without the compressor lowering the system pressure.
one can in, with the compressor running, the pressure on the blue (low) side should drop into a vacuum, or at least drop below 20psi. the can at 80°F should be putting out at least 100psi. more than enough to enter the system.
ONLY OPEN THE BLUE (LOW) SIDE WHEN THE SYSTEM IS RUNNING!!! (high) side pressures can rupture the can and kill you. also, high side will put things into the can, and they can cause problems.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!