Add to the low side. Add gas not liquid (have the can right side up).
Let the engine idle with the AC turned on.  Set the can in some hot
water to keep it warm so that its vapor pressure is more than what is
in the system.  When you get some in there, the compressor should kick
on and then the refrigerant will go in faster.  When the can gets warm
it's empty.  Two cans may be enough to get the system working but it
can hold more than that.  I don't remember the amount, but I think the
sticker tells you.
  Remember that a gauge can only tell you pressure.  If there is some
liquid in the system with the compressor not running, the gauge will
read the vapor pressure of the refrigerant at the current temperature.
 The gauge gives you no clue as to how much liquid there is.

Have fun,
Larry A.
  need to give my AC a little juice before we go to Texas this month

On 4/3/10, titantic01@aol.com <titantic01@aol.com> wrote:
>
>
>  Hello gang,
>
> Last year about the fist of April, I spent over $400.00 to get the A/C in my
> '87 vanagon going. a hose was replaced and some minor things were done.
>
> Now, a year later, I turned on the a/C and it was so low of freon that the
> safety switch would not even let the compressor run. I went and bought 2
> cans of 134 a and a cheap gauge dispensing set up to put it in with.
>
> My question is since the compressor won't energized will I need to some how
> jump the compressor clutch to make it run while filling the thing up or will
> it start on it's own once I have put in enough freon?
>
> The other thing I want to know is is 2 cans enough or does that system take
> a 3rd can?
>
> Thanks for your words of wisdom on this.
>
> Happy Easter everyone.
>
> Chris
>