well if the directions that came with it are too technical heres what I know from my own limited use: Bottom left settings are going to be the most useful to you in measuring current draw from battery with power off. you'll disconnect neg term of battery and measure draw from battery by completing the circuit with your multimeter. looks like you'll plug black wire to COM and your red to either mA or 10A and see what your readings look like. Then start pulling fuses one by one and see if anything looks funky. Another piece of advice, go outside and play around with the multimeter. you are probably going to figure it our quicker if you scan the directions once and go try it out, I bet you'll figure it out.

I had a vacuum pump for my central locking system that drained my battery every night. I could hear the thing going with the car off but the multimeter helped me make sure that was the problem (pulling fuse showed less draw on battery with car off than with fuse in place).

good luck,
cdt

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2002suzukiGSF600S
1985 190e 2.3