Installing AUX light on GC2400

[BXpanded]

Fuses are almost always intended to protect the wiring in a circuit, not the device being powered. The electrical engineers that worked on this tractor would almost certainly not have installed a 15 amp fuse if the wire could not handle that much current. Still, a few calculations indicate that 15 amps through a 5 foot length of 18 gauge wire would produce about 8 watts of heat over the entire length of the wire. That's about the heat from a normal flashlight bulb. Also, the voltage drop over the same wire would amount to about .2 volts. Neither the heat nor the voltage drop should be of any significance, with three 55 watt lights.
Due to the wire lengths involved, comparisons to house wiring are not appropriate. I have no idea as to the origin or reason for the 70 watt statement . Please, one of the E.E.s here, check the numbers.