high voltage stock 6.1 alternator

Regulator is free of paint. I also soldered an extra ground wire on the regulator.
Did what I said above. Voltage dropped a bit to 14.8. But on 15.4 again as soon as I switch on lights. Or wipers..... funny is that I measure less voltage on the starter Relais than over the battery terminals. About 0.5v less... well, I am feeding the whole car from there.