Can't figure out an electrical draw?

I found that the previous owner of my daughter 66 cuda had wired the tach to constant 12v, instead of switched. The tach + memory was drawing 0.3 amps (300 milliamps). Fixing the tach dropped it to 0.08 amps (80 milliamps) Get a $4 multimeter, the red digital one, from Harbor Freight. They can check amp draw up to 10 amps.