Just to be clear "with all electrical 12.49" is engine at 2200rpm and everything turned on, right?
If so, that suggests a weak alternator. But, 30m after shutdown 12.67v is right and good. Likely two problems.
Multimeter amp draw time. Unfortunately I can't tell from your picture how to do that with your multimeter.
First, we discussed how to use a multimeter for measuring voltage, or simply verifying that voltage is present. Last week, we addressed measuring resistance—verifying that a wire is continuous and not broken somewhere. Today we’re discussing how to use a meter to measure current, also referred...
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Broadly speaking, put the meter into amp mode (plugging in the probes where appropriate, usually on COM and mA), then remove one fuse from the fusebox and put the probes from the meter across the two terminals of the fuse receptacle. If the thing on the other side is drawing power, it will register as (milli)amps on the meter.
Opinions on acceptable parasitic draw varies, but 100mA is probably the tippy top. I would expect a c900 to be quite low - 25mA or lower.