I was vacuuming the residential refrigerator system with 3CFM pump that I've got from Harbor Freight Tools using Supco Vacuum VG64 gauge. Pump was brand new attached through copper hose to suction line, vacuum gauge was connected using one of the gauge manifold flex hoses to high side line. Vacuum gauge stops at 1100 microns and never goes below. After 30-40 minutes it even starts going up to 1200 microns (probably because pump is getting hot and inefficient). I tried to blow it through with dry nitrogen and to do all over again but no results. I purchased new Battery for vacuum gauge but still nothing gets better. I was wondering if I do something wrong or it's bad vacuum gauge?