Ed, your hypothetical scenario has a problem. Although power is current*voltage, it is really current time *voltage_drop* across the fuse. The voltage drop will not go up unless the current goes up.

Bill Schertz
KIS Cruiser # 4045
----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>

Here is a hypothetical scenario - lets say your alternator decides to go west in a failure mode that produces 40 volts (yes, there is an overvoltage failure that can produce voltages approach 60 -100 volts). Since you fuel pump will draw the basically the same current (perhaps a bit more with the higher voltage) the power across the fuse (Power = current * Voltage) will jump approx 4-5 fold.  (It is the power rating rather than current that causes a fuse to blow by the way).  You have just blown several fuses - could be critical ones.  Your alternator has died or you have disabled it and you could make it on the battery - but, fuse is blown.  Circuit breaker reset and one of your two redundant circuits (perhaps both) may work again. Just a hypothetical scenario.

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