I am pumping down the A/C on my '84 7-passenger this afternoon.  I have put in a new receiver drier and put the old o-rings back on.  I am using a 140 L/minute vacuum pump with a supposed ultimate vacuum of 10^-2 torr.  The only vacuum gauge I have in the one on the low pressure side of my gauge set.  I am pumping down on the low pressure side of the system and I am using 1/4 copper tubing between the center port of the gauge set and the vacuum pump.

How long should I pump down the system?  It had been exposed to atmospheric for weeks and I apparently iced up when it wouldn't cool anymore last summer.

John Lauterbach
Macon, GA
'84 7-passenger