We have some real electrical wizards participating in this thread, so let me ask a "somewhat" related question. I have two Ford diesel tractors (12 V) and used to have a Ferguson diesel. Every few months the engines will not start due to a build-up of a thin, flat black glaze on the positive battery terminal. I remove the positive battery cable, clean the terminal end and the battery post, reattach, and all is well for a few more months. This condition happens with new batteries and cables, as well as old ones, and can occur if the tractor hasn't been started for three months, or if I just shut it off three minutes ago. It is definitely not a loose cable issue, and it never occurs on my gas-powered machinery. I presume it has something to do with the fact that in a diesel engine there is no current draw after the engine is started, but I'm curious about the technical details of why it happens.
