The ammeter is useless because it is a shunt-style ammeter and therefore has very coarse resolution. You cannot use it to monitor minute changes in the charging system's output because it is masked by the coarse swing of the needle. The total current in or out of the battery is not what the ammeter measures; it only measures a very small portion of it through a secondary smaller wire (hence the name "shunt").

An ammeter is not the proper tool to monitor a charging system. Obviously it's useful to know if a system is charging or discharging, but that is only relative information. Watching an ammeter tell you it's discharging does not tell you how close the battery is to depletion on an absolute scale. This is something only a voltmeter can tell you.

Contrary to your claim, a voltmeter can tell you if the system is charging. If the voltmeter reads below the battery's steady-state voltage of 12 volts, it's discharging. If the voltmeter reads above steady state, it's charging.

Because voltage is what the voltage regulator uses to regulate current into the field terminal and control alternator output; voltage is what you want to be looking at anyway when diagnosing charging system issues.

 

And that is the definition of getting *owned.

Thanks for putting it out there FMC400

Josh

 

My bad on that. Being a licensed electrician my brain gets stuck on AC power with an unlimited supply of electricity. Of coarse with a limited supply of electricity as your using more wattage then your producing you will have a voltage drop.


What are you twelve?

 

A 12 year old that fully understands automotive electronics apparently.

Josh

 

Dude not looking for some sort of argument just seemed a little childish to me thats it.

 

I put a "new" entire dash\instrument cluster out of a late eighties ford van in my truck last month. The ammeter needle moves between midway and 3/4 of the charging side of the guage at night with the lights on while driving, and back to center while idleing. It moves about 1/8" total from center deflection during the day while driving. By that I mean, it goes to the right about 1/8" and back to center while depressing and letting off the gas pedal after start up and before the battery is fully charged.

I love it, just because the needle moves.

 

No worries. I have the same issue when I switch gears and go from working on the truck to working on the house.