It's an unusual circuit. And there are several known vulnerabilities in Sevens, including the variety of alternators and problems when the warning light is an LED rather than an incandescant. Check all of the connections at the alternator and try to find the Brown/Yellow wire. Measure the battery voltage at rest, minimum during cranking, and at 3,000 rpm, and post the values. The last of those will check whether the alternator is charging properly. Jonathan