I had a similar problem, had 2 techs look at it to no avail. Finally sat down and examined the whole circuit, at the end it was a bad connection where the blade connectors fit in the alternator.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.