I think if it were mine I would monitor the load voltage while having my DC Amprobe monitoring the load amps at idle...then slowly increase the RPMs sitting there until it gets within an amp of blowing the fuse and see what the voltage actually is. Two things come to mind. One, CFM has the worest electrical components. Even a straight connector has resistance through it. High resistance on a connector can effect load amperage...just as low resistance on the load take it closer to a short. Is there one light burning brighter or dimmer then the other? And two, if the voltage starts normal..say 13.4-.7 and increases over 14.8..say 15+, then I would say there is a regulator issue. If all stays in range and does not blow the fuse sitting there then it's a harness issue that only happens in motion..IMO. I'm not going to suggest you do this but if it were me...I would double the fuse size and look to a hot or burned spot in the harness or connector..if all else fails. You did not hear this from me as it may cause a fire...so be prepared.