There is literally not much to a starter relay. Inside is a pulling coil and a set of contact points. Mine failed a couple years ago so I sourced an NOS replacement. Once the car was up and running, I was curious and disassembled the original 55 year old relay. There was no rust or corrosion inside, except the contact points looked a little dirty. I dragged a flat file across the points a couple times to clean them up and tested it numerous times using a Milwaukee 12 V battery. It worked every time. The original relay got put back together and saved in my box of spare parts.
