[Excaliber]

Even with the fans running the Amp gauge should NOT be showing negative current drain. If it is there IS something wrong. Amp guages are not "that accurate" and to measure actual amp draw (37-74 or whatever) you would need a more proffesional gauge.

Bottom line: Assuming the fans draw 75 amp and the alternator is rated at 60 amp. THEN you will see a 15 negative drain. In that case you need to "up size" the alternator or limit fan run time.

But 45 amp drain? Nope, something is way wrong with this picture. It MAY be as simple as the Amp gauge cannot be (and should not) be "fully trusted" for accurate readings.