alternator woes

[jmc <jmc987@earthlink.net>]

Since I converted my MGB to negative ground about 2 years ago, I've been 
through at least four alternators. (I'm not even sure. I've lost count.) 
With the latest one, the ignition light doesn't come on until the engine 
is running and only goes out when it's running at about 3500 rpms. This 
one's a Lucas unit rebuilt by Bosch. Any suggestions on what I can do to 
fix this one and/or keep it from happening again? Thanks in advance.

Joseph
67 B Roadster