Testing for voltage across fuse terminals is not valid. In a circuit you will measure full supply voltage across an open only if the circuit is complete the rest of the way.
Think of it as a light bulb, switch, fuse, and a battery. With the switch turned off you would measure the battery voltage across the switch and not across the bulb or fuse. If you close the switch and remove the bulb you would measure the battery voltage across the bulb socket. If you remove the fuse, the only way you would measure voltage across the fuse contacts would be if the switch was closed and the bulb was good.
A better test is to measure from ground to each side of the fuse holder. One side should measure the 12 volts. The other side will be zero. Ohm out the fuse before you put it back in. It should read near zero ohms which means it is good.
If you measure 12 volts on one side and the fuse is good but nothing powers up in that circuit, you may have a bad fuse connection or open in the line from the fuse panel to the load. You could also have an open in the ground side of the load which would give the same symptom.
Retired electronic technician (45 years in the field)
2017 Greyhawk 29W
solar & many other mods
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