The Stovebolt Site Forums The Shop Area The Electrical Bay Amp Gauge reading

I have a 58 half ton with a 12 volt system.My amp gauge needle in on the center dot while running or on the road with high rpm. When I turn on the headlights it moves back just a bit toward the discharge.Should it not move toward the charging side while running hard. The ohm meter shows 13 volts at the back of the alternator and 12 volts from the battery while running. Is this a normal reading for the amp gauge.

I'm no expert but I think you should be putting out closer to 14V (13.7 or thereabouts). The only time your ammeter should be showing a discharge is with the engine not running or at slow idle. If I'm wrong on that someone will correct us both shortly.

your alternator could have a slightly low output, but sounds like things are OK, remember these gauges aren't high tech, just general indicators, you need to learn what's "normal" for your particular unit - the ammeter should show a definite discharge when the battery is low [like immediately after starting], then snap to at least a slight charge once the truck is running, and come back to around neutral after running a bit and the battery is back to full charge

Bill

That is how it was operating until it sat for about a month. When I would let it idle the hand was at the center dot and when the engine rpm was increased the needle would jump just past center toward charging and after a few seconds come back to the center dot. I have a new battery and new alternator.Belt is new and it starts right up when I press the start button. This is just a little off from where the needle would surge at sudden rpm increase.Even when the headlights are turned on there should be a sudden discharge then the needle should return to the center dot if running past idle. Does this sound right?

yes - the jump when turning on the lights shouldn't be more than just a jump, down and back, that's just the delay in the regulation reacting to the current draw change .... if it's acting a bit different since changing the alternator it's likely the regulator [internal] or alternator itself being a bit different .... a good auto electric shop [or maybe the store you bought the alt from] can check the system under all conditions to see if it's working properly, and maybe adjust it if necessary

Bill

How do you test voltage with an ohm meter?

I agree it is working fine. The Gen/ alternator will only mantain a charge in the battery. Not enought to move an amp guage much most of the time. A country boy check is to turn your lights on for a couple hours and discharge the battery. Start it and it should then show a 20 to 45 amp charge.

It is a multifunction volt meter that I use for checking restistance. I can switch it to ac or dc current also. I used the term ohm meter because that is what I use it for mostly, but when I'm to lazy to walk back to the shop for the electrical tool box I just swap it over to dc current and measure the current.