This paper presents an experimental investigation into the shear capacity of prestressed concrete (PC) hollow core slabs with and without pre-existing oblique crack damage. A salvaged hollow core slab from Taihe Road Viaduct was selected for testing, with one end exhibiting in-service crack damage (T-A side) and the other end remaining intact (T-B side). Both ends were subjected to static loading to failure, and their shear performance was compared. The results indicate that the ultimate shear capacity of the damaged T-A side was approximately 16% lower than that of the undamaged T-B side. The damaged end also exhibited a lower cracking load, greater ultimate deflection, and greater torsional deformation. Both ends failed in a "bond-shear" mode, but the presence of pre-existing cracks on the T-A side exacerbated crack propagation and led to a wider main failure crack. The experimental results were used to evaluate the accuracy and applicability of several shear capacity calculation methods, including JTG 3362—2018, AASHTO LRFD Specifications 2020, ROSS, Naji, and Zhang''s models, and the Response2000 program. The comparison reveals that Zhang''s model and the ROSS model provided the most accurate predictions relative to the experimental values. The AASHTO LRFD method was found to be slightly unconservative for the damaged side (V_t/V_pre = 0.94) while providing a conservative prediction for the undamaged side. This study highlights the detrimental effects of in-service cracks and reveals limitations in some conventional codes for assessing damaged members.