Watch-out For The Big Bang
Brother of The Benz, Jeepboy
I don't know what size A/C unit you have, but my 1987 300E uses 2.2 lbs(35.2 oz) of R-12.
In retrofitting to R-134A you decrease the capacity by 15%.
My system then uses 1.87 lbs of R-134A or approximately 2 1/2 12 oz cans.
If you installed all three of the 12 oz cans or 36 oz total into your unit, you may have it SO OVERLY charged that something has to give and it can be quite costly and dangerious.
Determine the proper amount of R-134A required.
I may require emptying the system and starting over.
You won't have to had additional oil, although you may consider adding the dye/stopleak additive, and just the proper amount of gas.
Here's hoping you do your homework.
Happy Trails Beep Beep from The Spiderman in Houston!!!