Me too.
My guess is that the light goes out when the alt is working. Like most cars.
Check the sense wire to the v-reg.If that is bad the reg will tell the alt to get going.
The best contact cleaner I've found in forty years is WD40 and scotch brite.
Looking at my bat pos cable the other day the terminal came off with a slight tug.
Where did you find a wiring diagram ?
Just wondering, Why a 90amp alt ? That's a lot of current.
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.