By John Smith
A large car manufacturer in the UK was pulling out their hair trying to find why one particular rear wheel drive vehicle was getting through rear-wheel bearings every few thousand miles.
All the boffins tried everything, even changing the back axle, with no luck.
An apprentice suddenly opened the bonnet (hood) and saw the problem - no grounding cable from the engine block to the chassis.
Every time the starter operated, the return current ran through the ball bearings in the rear axle back to the battery. The arcing was pitting the ballraces, causing them to fail.