Air conditioning - recharge kits

I have a 99 Bonneville and a 97 GMC tuck - the AC in both seems to blow cool, but not really cold - anybody had any luck with those self service kits with the guage and R134A where you top it off yourself ? Anything I need to beware ? Thanks!

While it may work, it would be much better to have it checked first to determine the condition and if that is good, fix any leaks and do the job properly.  In the long run I believe you will find that cheaper and more satisfactory.

I have used them with some success. My car had a very slow leak and one can of the R-134 would keep it going all summer. If your system isn’t holding pressure at all, you might as well bite the bullet and go to an a/c pro and get it fixed right. By the way, I compared the system pressure (low side only on the can gauge) with a professional set and found them very close. YMMV.

well, the thing that puzzles me is that the one in the truck has always seemed to not get real cold,but works OK - but I have had it 5 years and it has not gotten any worse (the truck is a dark color and has leather seats - I iamgine it takes longer to cool down ?)

the Pontiac - I bought new in 1999 and as recently as last September would get so cold you had to turn it down - it is white and has cloth interior - seemed to cool faster - last Sunday when it was about 82 degrees out, it seemed to cool like normal, but when the outside temp got up to about 95 it cooled but not so good - outside temp should not matter, should it ?

one other thing - the low pressure side is the one closest to the firewall, right ?

Generally the fitting next to the firewall is the low pressure side.
The 134 service ports are different sizes so you cannot get the high/low sides crossed up.

If the system seems to be taking the charge slowly, try palming the can. The warmth from your hand should help it a bit.
A pan of hot, not boiling, water can also help evacuate the can faster. Keep the water level about 2/3 of the way up the can.
A cheap pair of safety goggles is always a good idea; just in case.

Why do you assume that the system is low on charge? Have you checked the operating pressures to verify the system is low?

There are other things can can affect the temperature output. One thing that is overlooked is the condensor, have you checked to see if the condensor is plugged with debris?

Adding freon to a system that is not low can cause more problems than you started with.