QuestionThanks Howard - I have an MGB. I think you are bang on correct about the heat gauge - makes sense. Past damage to the ignition has probably been cause of smoke I saw. I will be testing the charge immediately, and let you know the result. And if I find system overcharging, then as you say, heating up has perhaps damaged the wiring ...if so Is there any way to tell extent of damage and whether loom needs replacing?
AnswerIf your car was brought to me in a dealership, I would first test the alternator. Put a volt meter across the batteries (or battery if you have converted to one 12v battery) and read 12v +.
Then start the engine and set the throttle at 1500 RPM and read the voltage. It should be (13.8v to 14.5v) but not more. If it is more you have a alternator problem or a regulator problem. If you find it high, that could be the cause of your electrical problems.
Look at the wires under the dash and under the hood to see if you see any sign of melted insulation on any wires.
If not run a test of the operation of every electrical item and if you have several failed items pick the easiest to trace. This is where the diagram is needed. http://mg-tri-jag.net/74MGB11x1.jpg for the diagram and change the suffix to 74MGB21x1.jpg for the index to the diagram.
The one circuit you decide to trace start at the "Load" (item that don't operate) and follow the diagram toward the "Source" (battery) and only go one connector at a time. testing with either a 12v test light or a volt meter. This is a 100% correction and can not fail. Many times when I have several circuits that have failed, when I correct the one I pick to trace I usually fix all of them at once.
If you find a loss of power between connectors then it can be inside a harness and a trace of one more failed circuit nets the same, then that is a good sign of a melted harness and you have to either strip that harness or purchase a new harness. This is rare but can happen.
let me know,
Howard
