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Someone want to explain how the ammeter showing + (charging) somehow means it is low on output?

If it showed - (discharging) then yeah.

Do you have anything else being powered directly from the battery, such as an electric fuel pump?

Fluctuations means it's cycling the charge to the battery, assuming there is nothing wired to the battery non-stock.



If alternator output was enough not to ever discharge the battery, the ONLY time the ammeter would register charge would be right after cranking the car (to refill battery from starter motor).

If the ammeter is reading charging while driving, this means that at some point (maybe at idle) there was a discharge from battery which must be replenished when the engine/alt is at higher rev's.

I can see this all the time with my ammeter...slightly discharging at idle when at a light then pegs the charging side for a few secs after taking off due to replenshing the charge used to fill the shortcomings at idle.

If it shows charging regularly off and on during driving (esp after idling for a while), you are losing dicharging. This could also be falsely read if there is some other non-stock load on the battery side of the ammeter.

As the guy above mentioned, anything else drawing from battey? Fuel pump maybe? If not, you are discharging slighly at idle.