And I thought I was being clever!? Measuring DC amps via fuse socket help!

Well... I must be missing something.

A long story short, I'm looking at getting a start/deep cycle marine battery for my little ute.

It only gets about 5000km on it a year and can sit for a few weeks at a time. I'm noticing the battery is degrading a little early as it's not getting used enough. The other side of the coin is that it would be good to run the radio while I'm working without the worry of draining the battery so I cannot start it.



So I thought I was being clever by measuring the actual Amps that the radio draws and match a battery size. In my mind, the simplest path to go would be to pull the fuse for the radio and meter it from there... Except...no go! The meter closes the circuit and the radio runs but I'm getting a reading of 0.00DC amps.



Any ideas why it's not working?



I tested the amp function on the multimeter on both DC and AC as well as both and it's fine.

I'm using the 10A fused side set to DC.



I will test it again via the battery as I know this will work. I just thought I was being clever doing it via the fuse panel. That way I can adjust the volume, key and radio all from the cab.

Any ideas why it did not work via the fuse socket?

It's got me stumped!