In most cars, battery cables, like the Purloined Letter, occupy positions under the hood so much in plain sight as to remain invisible. In any case, the driver may check the oil and transmission fluid levels, the windshield washer reservoir and the coolant overflow container with only a cursory glance in the area of the battery (or batteries in some vehicles). The vehicle started up just fine this last time; why should it experience a malfunction in the area of its electrical system?
Even if the driver does look down at the battery and its two cables, he or she may not observe anything out of the ordinary. In the majority of cars, battery cables outlast the driver’s ownership of the car and may work fine right up to the day the car becomes fodder for the parting out industry. Manufacturers generally fabricate the cables of superior quality wiring protected with durable sheaths of heavy insulating material. They design this critical part of the vehicle to last.
If ignition problems do develop, however, and the driver (or qualified mechanic) can eliminate all other areas of the electrical system as the cause, the battery cables should come under close examination. This may require removing them from the engine compartment to facilitate the inspection.
First remove the negative cable from the battery. Look for a negative or minus (-) sign on the battery or on the cable. (Identify the positive cable by its red color or by a plus (+) sign.) Remove the cable by loosening the retaining bolt that clamps it to the battery post; avoid forcing the cable free. Follow the cable back to the engine block and loosen the bolt that attaches the cable to the block.
With the cable free turn it around in your hands and scrutinize the insulation along its entire length. Look for breaks or excessive wear. Wear often occurs where the cable bends over an edge of the battery. Look for signs of serious corrosion on the metal parts of the cable. These and similar defects may remain invisible to casual inspection, but easily can cause a disruption in the ignition process of starting the vehicle.
Examine the positive cable in the same thorough manner after removing it from the battery and from the starter solenoid. A definitive test of the battery cables may require installing new cables (with contingency of returning them if ignition problems still persist); if the vehicle starts OK, this will prove one or both of the old cables had failed.