It could also be the fact that it didnt work before because it had no R-134a in there and after only adding a little to get it going, its still not up to proper specs and pressures and thus the computer thinks its gotta keep going.

I'd personally take it somewhere and have them do a simple AC system check, and see if there is a problem somewhere. Then if non are present fill with the proper amount of R-134a and then all should be good.

Most places do cheap system checks this time of year.