VERY UNLIKELY that you will overheat the amp gauge. It consists of a shunt that serves as a slight voltage drop that the actual gauge measures that voltage drop across it. I suppose if your alternator exceeds the rating of the amp gauge it might peg the meter, but unless you've exceeded the carrying capacity in amps of the wires connected to the amp gauge, you don't need to worry about overheating. If you're worrying about that, you can connect the alternator output wire to the battery side of the amp gauge, but then you'll have no indication of whether your battery is getting charged. Same with a high amp load, like the electric fan, whose circuit feed can be connected directly to the battery (put a fuse in that connection for protection.)
