My voltage does increase when revved and I am getting similar readings to yours. It looks like it is normal for the fan to put a big draw on the electrical system. Thanks for sharing your readings.Krup327 at a stop,with the brake on and the fan running there is a big drop in voltage. Even with just the fan running it pulls a lot of volts. But it is not really normal for the volts to drop more when you increase the RPM's to 3000. Your reading should go up when you REV up the engine. Mine at a stop and the fan running the volts can be from 12.6 to maybe 13, at times even lower with the brake on.