What does red mean- too much pressure?  That would indicate some sort
of blockage, I should think. How that could happen on the low side of
the system beats me. Maybe it was overfilled in the past?
-Paul

Now... how can I avoid telling you how inferior these cans are yet tell you
how to reliably and effectively repair your system?

Your can "tells" you that there is a serious problem with your system....
Taking the can back for a refund and having the system repaired correctly is
a viable option.

In the shop, we use some simple tests to determine our course of action...
none of which include "topping off" the system. If the system is low there
is a leak. Without proper testing, there is no way to judge the severity.
There are other possible causes as well. Without the proper knowledge you
run the risk of adding more damage to the system as well as releasing
compounds into the atmosphere that could affect future generations.

For troubleshooting, I can only suggest that you gain a working knowledge of
the system before you attempt further repairs.

Make sure that you are connected to the "low" side of the system.  On
my 93 it is on the paassenger side, near the fuse box and has a blue
cap.  

Is it red showing high or red showing too low a pressure.  When you
lose freon it can make the low side go lower and I suppose they could
show that as a low side red zone.  If you feel the metal parts of the
hose assembly as each pipe comes out of the compressor the high side
should be hot and the low side should be relatively cool to cold.  You
can also feel the pipes where they go into the evap case by the
firewall.  The high pressure should be hot just before it gets to the
junction where the orifice tube is and on the other side of the
orifice tube it should be cold.   If it's not pretty hot right on the
inlet side but seems relatively cool it could indicate a restriction
upstream in the high side.  Don't recall if you can feel both sides on
the 94's, I know I can on my S-10.  You can also feel the outlet pipe
from the evap and it should be roughly the same temp as the cold side
on the input side.  My memory says that if it seems significantly
warmer in the outlet it's probably low on freon.

The other thing to look at is the amount of cycling the system is
doing.  If all is well and you run the engine at 2000 rpm and it's a
moderate temperature day the clutch should cycle several times a
minute.  If it's really hot it might not cycle at all unless you are
spraying water on the condenser.  They cycle when the low side
pressure drops below around 24 psi and come back on when it goes up to
about 40 psi.  The pressure is pretty close to the temp the evap core
is at.  So you see if you average 24 and 40 you get right at 32
degrees.  Just at the freezing point of water.  If it gets low on
freon the pressures go low and on moderate temp days it can make the
core too cold and that's why cars with low freon charges may freeze up
on moderate temp fairly humid days.

Well turns out the system was actually low on R-114.  The reading on
the cheap gauge was not accurate because of an issue with the low side
tap on the evaporator.  
I found my hoses that goes to my gauges and hooked them up.  Seems
that there is an issue with the needle valve on the evaporators tap.
Weird though as I cannot replace that valve.
Isnt that valve replaceable on 94 Evaporator???  I tried backing it
out but the needle valve tool that one uses to back the needle back
out caught onto nothing and it did not turn.  

Needless to say once I charged the system the A/C was cold again.

Now I am worried about the low side tap leaking.

I guess I need to buy another evaporator since I cannot get the needle
valve out to replace it????

Making progress...at least the air is COLD since this week the temps
will be 100 with heat indexes of 110.  Just worried about the system
leaking over time.

Sam in Raleigh.

Thanks everyone for your feedback!!!