importance of testing with a load

An aircraft owner troubleshoots an electrical circuit that is not working.
He disconnects the load to gain access to a convenient place to connect his digital volt meter. The digital meter reads 10 volts.
The owner's friend who came to help, tests the circuit with his cheap antique analog meter. His meter reads 0 volts.
Which meter is correct? Answer: They both are. Why? Because the digital meter has very high internal resistance.
The analog meter has much lower internal resistance which loads the circuit.
If the aircraft owner had not disconnected the load, both meters would read the same.
An electrically challenged troubleshooter might be better off using a TEST LIGHT.

I keep an old incandescent test light around for these situations. Even the modern LED test lights can give a false positive because the current requirement is so low to get the LED to light up.

Why is blown fuse resistance 2 Megaohm rather than "infinite"? (in which case the digital meter would be expected to read 0 volts)

Every blown fuse is different. Some might have infinite resistance.
Others have some measurable resistance, enough to confuse a troubleshooter.

Or the 'fuse' is one of those electronic ones. Definitely not infinite resistance. Drove an acquaintance nuts. What? Every wire has power???

Thank you. There is always something new to learn on VAF!