97 Jeep Cherokee, air conditioning compressor cycling on/off and weak cooling

I have a 1997 Jeep Cherokee with factory air and about a year ago I
noticed that the air was getting wimpy to the point where it just
wasn't cooling anymore. This year I went to the local auto parts place
and picked up a R-134 kit to recharge my system (figuring it was low
and had a small leak). I hooked up the gauge that comes with the kit
and read the value off the low pressure side of the airconditioning
system and (from what the kit instructions say) the gauge read about 45
psi (which is supposedly good for most low pressure side readings -
they say that's normal). No matter, the compressor regularly turns
on/off - about 10 seconds on and about 10 seconds off - - - all the
time. I just about put in some R-134 and then figured I better get on
the news groups to see if this is normal or not with this rig. The air
is just lukewarm - not quite cold, not quite warm either on an
especially hot day today.

What do you guys think? The system low pressure reads right (doesn't
surpass 45 psi and just sits there) but it's not getting cold either.
What's the correct pressure reading for this system and what do you
suspect is wrong? The vent system is correct (I checked that). Thanks
in advance for helping out, guys.