Transient Suppression Diode Link (for techies)

Reverse bias the rectifier, the cap is electrolytic so polarity needs to be observed as well. At the starter motor side of the solenoid, will do fine. Double encapsulate both discrete components in dual wall heat shrink tubing, make a service loop on each side of the encapsulation and you're home free. Remember NEGATIVE transients are involved as well. This kills them dead.