Triumph Repair: Spitfire 1978 Electrical Problems, head lamps, hi tim

Question
Hi there

I have been experiencing a strange problem for the past couple of years and I need to get it sorted out. After driving for about a half hour the car will die. And I mean die. There is nothing coming out of the battery that will drive anything like head lamps, radio, or whatever. I have to tow or push it back to my garage. The strangest thing is that if I let the car sit, I may come out after several days and see that everything is working just fine again. I have tightened up connections like battery and ground but no solution. It has stymied most people I've spoken to who are suggesting a ground problem.
Does this make any sense to you? By the way, the electronic iginition was replaced on the thing 25 years ago.

Answer
Hi Tim,
This should be an easy one to diagnose. You need it in the failed mode and just put a 12v test light across the battery posts (NOT the cables) If you have no power at the posts then you have a bad battery. Period! If you have power at the posts and not at the cables you need to remove the cables and clean the posts and the insides of the cables as they can be at fault even if they were tight. It is no use testing when it is working, all tests MUST be done while the car is in it's failed mode.
Howard