Q: My negative battery cable start smoking when the car is running.

There is a faulty, high resistance (often due to corrosion, wire defect or break or loose mechanical connection) connection at the battery post and/or at the vehicle ground(s) at the frame. The recommended and safest practice is to replace the cable (cables can corrode within and cable crimps at the cable ends can’t be serviced without shortening the cable). When replacing, particular attention should be paid to the cleanliness and quality of the vehicle ground connection. This is a safety issue and consequently the repair is recommended at your earliest convenience. If you desire mobile service on this repair, the service to request is battery cable replacement and the responding certified mechanic will deal with it promptly.