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When I bought my car, Ross Miller checked it out and as part of the inspection told me my voltage regulator (VR) was not charging correctly. He adjusted it and I was on my way. Here it is a couple of years later and the ammeter gauge was fluctuating wildly. I had a new VR so I decided to install it.
As part of the testing, I had to make sure my battery connections were good and the battery water levels were correct. Well, the cells in the battery were half full! EEK! So, I filled them with distilled water and went for a test drive. I checked battery voltage when I returned and it was 6.25 volts.
Here is what is happening and I was wondering if it is "normal".
At idle, the gauge is just slightly to the left of the center of the gauge.
When I drive, and use the turn signals, there is a big swing to D.
If I turn on a small draw like the heater motor, it almost pegs to the D.
With the engine off, and the ignition on, the needle is little to the left of center.

Data
Specific gravity all cells 1.300
Voltage at terminals 8.4v (after overnight charge)
Amp Clamp readings
AMPS
With just heater blower motor on 5-8
Headlights only high beam 18
everything including radio 38
just turn signals 5-10
Question: Is the ammeter working right?

That is a good question and I have almost the same experience but on the opposite side. Mine seems to behave with needle moving slightly to the discharge side with key on and about halfway with the headlights, heater or AC motor running and pegs with them all on. Mine wants to peg the charge side when the engine is running yet I measure an acceptable charging current. Maybe someone else who has a working 47 can let us know how theirs behaves so we can both be enlightened. I bought a new regulator too but have not installed it yet because I am thinking of installing a Powergen alternator which won't use a regulator..

Packard goes to great lengths to say it is a battery charge indicator and not an ammeter but still both seem to be working oddly -- at least mine is compared to the 56 which they also say is not an ammeter.

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The more critical question is does the gage ever indicate "C" ie charge while the engine is running? Reading your description it seems not, which tells me either the generator or the regulator has failed. REad your battery voltage while the engine is running at a high idle and nothing extra turned on. I would like to see 6.8-7.2 or so.

One thing with batteries, they must be checked with a substantial load. That?s why in old times when each segment of the battery had two poles to measure and a fork looking device with a load resistance was used.
If measuring without load with a voltmeter it will indicate correct voltage even if the battery is totally shot. If You do not have the proper tool use a voltmeter at the same time as when as many users as possible are active. The voltage should still show around 6 Volts.

Reporting a specific gravity of electrolyte in all cells of 1.300 (probably more like 1.285 which is about max) shows that the battery is fully charged with no weak cells. At static rest the voltage should 6.6v.

It's my understanding (correct me if I am wrong) A battery can indicate, after charging, a fully charged state. BUT ....a carbon pile (load tester) needs to be used to remove the "surface charge" so a meter shows more accurately the charge of the battery and the recovery of the battery. If you don't have a load tester, prevent the engine from starting, attach a volt meter to the fully charged battery, crank the starter for 20/30 seconds I'm sure with the starter pulling 300amps out the state of the battery can more accurately be determined.
Two things needed for a good battery.
l. sufficient charge
2. The ability to operate the load of the car and recover rather quickly to repeat the demand. I hope this helps.
Steve

Actually Packard preferred using a hydrometer to determine battery condition and stated specific gravity over 1.225 was a sufficient charge. Attempting to get something higher by overcharging may not be a good idea. (I know ... The books all say that 1.265 is 100% and 1.225 is 75% but I'm only following the manufacturer here).

For load testing they wanted a cranking voltage of 4.5 with the ignition disconnected, or 1.5 per cell. If one cell is significantly lower the battery has a problem. On those old six volt batteries the external poles allow testing per cell. But if one cell is bad it should also have poor specific gravity.

Tim, thanks for the information.
Steve

Update.
I keep a battery tender on my battery. So, I took the car out just now. Regardless of speed, the needle stayed in the middle. When I returned home, I attached volt meter leads to the battery and started the engine. It was around 8V at idle. When I raised the idle quite a bit, it went as high as 9.3v.

So to my simple mind, if it is a battery charge indicator and not an ammeter, it was behaving correctly to have the needle stay in the middle if the battery is fully charged.
Discharge spikes, when accessories are turned on, would make sense as when accessories are running, the voltage regulator senses this and diverts power to the accessories but that does not mean it is not charging the battery too.....so the car starts the next day..

Howard,
Wouldn't your indication of pegging at charge indicate some weakness in the battery...maybe cannot hold a deep charge? Have you measured the voltage at rest and with the engine running. Specific gravity measurement would indicate a bad battery too.

Of course, no one gets more shade tree mechanic than me! But the checks are simple..