I wired an ammeter by removing the existing wire from B+ on the alternator, attached one wire from the ammeter to B+ and the other wire from the ammeter to the wire just removed from the alternator. By doing this, it appeared to me that I had placed the ammeter in series between the battery and the alternator. Oh, I used #10 stranded wire. Sure enough the ammeter reads on the + side indicating charging and the reading varies according to how much stuff is turned on. However, the voltmeter now reads about 11 volts with nothing running other than the fuel pumps, instead of about 13.5 volts. Turn on lights etc and it drops to barely over 10 volts.

What am I missing? All suggestions cheerfully accepted. There isnt anything wrong with the charging circuit. I just wanted to add an ammeter.