[kobrabytes]

Love people who can produce a schematic!

The amp meter ONLY measures charging current in this schematic, and NOT the output of the alternator to the accessories. It will however measure the draw from the battery to the accessories when the car is NOT running.

Disconnect the R and N wires from your amp meter and use an ohm meter to see if you somehow have a grounded meter. (Gnd to + and Gnd to -)

Use an amp meter to check your accessory draw. Do it one at a time. You'll probably blow the fuse in your amp meter when you check the fans unless your meter is good for more than 20 amps. With the engine not running disconnect the positive lead on the battery and put the meter between the battery terminal and the cable. (Ignition switch on run)

Before you turn on the ignition switch is there any draw?

If you use an MSD multiply your reading by 6. THe AL's draw 1 amp per k of RPM

How large is wire N? Amp gauge to battery?

Does O (alternator wire have a fusable link in the case of a short?