volt gauge or not?

When I bought my car the previous owner had stuck a screw (yes, a screw) into the wire that feeds through the bulk head. When I removed the screw, the car would intermittently not start, go figure. The wire was burnt, so I did the MAD bypass and it's been fine ever since.

My volt gauge doesn't tell me exactly what my alternator output is but it gives me a pretty good indication if there's a problem?!? Approximately 12.5 volts at start up and 14.5 volts at cruise. If there's a variation, I start looking for the problem.