I have central ac and the unit outside is noisy ever since I had my quarterly maintenance. Could it be the "air handler" belt issue?

Sir,unless you have a package unit Meaning(furnace and a/c are all in one unit )on the out side,you won't here a airhandler noise coming from the outside unit. If it's a split system the airhandler is inside . And also unless it's a very old airhandler it probably doesn`t have a belt .trace the noise out better and give us more info.