Q: How to inspect and replace battery cables on Mercury Grand Marquis?
A: Inspect battery cables for damage like cracked insulation and corrosion. Check cable-to-terminal connections for cracks, loose strands, and corrosion. White deposits under the insulation indicate corrosion and need for replacement. Check terminals for distortion, missing bolts, and corrosion. When replacing, disconnect the negative cable first and connect it last to avoid shorting. Even if only replacing the positive cable, disconnect the negative first. Ensure the replacement cable is the same length and diameter. Clean the relay or ground connection threads with a wire brush and apply petroleum jelly to prevent corrosion. Attach the cable and tighten the nut/bolt securely. Before connecting to the battery, ensure it reaches the post without stretching. Clean the battery posts and apply petroleum jelly to prevent corrosion. Connect the positive cable first, then the negative.