Paul,
Our front AC unit decided to release some fluid out onto the roof (green/blue) it was either the Freon or the oil, (it was still working but it was only a matter of time). Either way I decided to replace it when I was told the AC units are no longer serviceable, this has been mandated by EPA, which made them tossers. So we replaced it and the rear AC as well thinking they are the same age.
Good luck with yours,