DeTomaso Mailing List: December 98, Message #8

{Note - this started out as an off-line e-mail to Forest Majors on some points he made on my car and possible cause of the problem, I decided partway through composing it to send it to the list to get as much feedback as possible and share the answers with everyone}

Now that price shock has set in on replacing this alternator, can I ask you a question about electrical troubleshooting? Thinking about the problem a little further, this alternator lasted a mere 5-10,000 miles before it died, it was a new one because the previous one died last year. That means 2 alternators in 2 years, maybe 10,000 miles apart. Which means either exceptionally bad luck or as you pointed out, an electrical problem somewhere. 

So that I understand how this whole system functions, please tell me if I understand the situation. The diodes in the alternator can get fried if current flows through them in the reverse direction intended, that I can follow. So if someone reversed the polarity when charging or jumping the car, the alternator could get toasted. What I don't understand is how a short could cause the same thing, mainly because I don't know enough about the electrical system and where current goes. If I had a short I could see if putting a serious drain on the battery and the alternator would not be able to keep up, my battery would die. Could a short kill the alternator? If so, how and where should I look? And as far as locating a short, about the only method I can think of is to get  test light or gauge and check the voltage at various places to see if current is getting through. That is assuming that it isn't just an intermittent short, of course, which means you have to catch it in the act too...

Is my logic fatally flawed or do I have the basic idea? Any hints?

Charlie McCall
1972 Pre-L
#3847
Still in France, not Pantera-less anymore!