Customized vent fan assemblies condensation issue?

[Tom&Shelly]

Oh, another idea...

Have you tried "slow-blow" fuses? The motors may (should, in fact) take a surge of current when they start up. Slow blow fuses are designed to more-or-less ignore that quick surge and blow if the steady state draw is too high. If the motors stop and start (like if there is a thermostat or something) a start at some more or less random time may be blowing the fuse.

Tom