I have a Ford NAA that used to do the same thing when the battery would get a little low or the cables a little coroded. If you are still running a 6 volt system it takes everybit of the battery to turn the engine over and a weak charge or poor connection will make the solenoid just click. Although not advised, I used to have to jump start mine from a 12 volt battery until I had it changed over to a 12 volt system and that solved a lot of problems...but it will still click when the cables get corroded. Good Luck!
TiminFallCreek, January 2011
