Dont know what ac pro is but assuming it is a can of r-134a, the low port will be in the low or suction side of the ac system, assuming the can you have came with an end to attach to the low side port, it will only fit the low side, the high side port will be bigger and your connector will not fit, I would suggest that you follow the directions on the can to a T, really though any a/c work should be done by a qualified tech with a set of gauges or machine to monitor the low and high side pressures,

Answered by PROTECH1980 (expert)
945 answers provided