If bell doesn't ring when you bring the two bare wire ends together, fault lies elsewhere -- in bell or chime assembly, wiring, or transformer. Remove snap-on cover of bell or chime. Removal may be harder than you expect; there are several different types of covers, and you may have to try several procedures. Try lifting cover slightly upward and then pulling it out. If this doesn't work, pull it straight out without first lifting it up. Or look to see whether snap-on cover is held to bell or chime assembly with prongs; if so, depress prongs and pull cover to release it. Whatever you do, never pull so hard that you risk damaging decorative cover.