AC Question

I was at the auto parts store today and i saw theres a product that seals the AC system of any leaks. the directions said to run that stuff through the system first then charge it immediately with the freon. i have 2 questions here, 1. how effective is this stuff, will it actually work? and 2. how do i know if my AC system has been converted to R134a????? i have one of those blue R134a guage things that i got from the auto parts store that i used on my pontiac and it also fits the valve on my caprice too, so thats why im questioning how i would know if its been converted, or are the R12 valves the same as the R134a ones? the system on my caprice has the red and blue caps also...

R12 hose connections are smaller than R134a connections. The R134a hose connections generally are color coded as well - blue is suction (low pressure) side and red is liquid (high pressure) side. The R12 caps are gray or black.

So i geuss mine has been converted then, because my R134a guage also fits onto the low pressure side valve too, good to know. i herd that they should have put a sticker or some label saying that its been converted, i dont see one, maybe they just forgot to or something.

I didn't use the sticker when I did mine, if that means anything. ;)

yeah the previous owner probably diddnt either. what do you think of that stuff that supposedly seals the system of any leaks though??? sounds somewhat effective, i dont want to waste my money though.