The Stovebolt Site Forums The Shop Area The Electrical Bay Understanding the ammeter

My 47 is still 6v. It runs great and I rebuilt the generator and installed a new voltage regulator when I built it 2 years ago. I rarely have it out at night but I noticed when I turn the headlights on the Amp guage moves to approxemetly minus 10 on a 0 to 35 scale. Does this mean that with the headlights on I am drawing my battery down or does this just show I am drawing amps from the system. If it is a draw on my battery, what do I need to do to resolve the issue and get my volatge regulator to properly balance things out?

Well first of all, you say rarely have it out. So battery may be the issue. Ammeter needle should show a charge for a little while then settle in center area. So two tests need to give a direction to go next.
1. Measure voltage across battery posts before starting.
2. Measure voltage across battery posts at high idle.

Report

Could just be corroded cable clamps, posts, cables, other connections. Neg and Pos.
Or of course, bad battery, bad charging components. Bad grounds.
Need the two tests first,

Dave,
Yes, you are drawing your battery down. You don't say what your engine rpm is when this happens. It is normal at idle. If this is happening while driving, for example high gear at 35 mph, that is not normal. If not normal then follow Bartamos's advice.
Kent

Kent is very knowledgeable in that era and others. He does extremely fine work. I visited his "auto museum" when he was kind enough to give me a TF part.

I said I don't have it out at night much. I don't use my headlights very often. I will do the suggested test. I will also test drive and see if it does it at higher RPMs. I was parked with it at about 1000 RPMs.

Ok I misunderstood. Now that I have re-read....Do you have "normal" ammeter readings in the day? How many hours per week/month?

Repeating what has been said......Other than the starter at 300+ A, the headlights draw the most. With sealed beams about 100A on hi beam. The battery will get recharged pretty quickly after start. The old faithful test is during the day, drive it and observe ammeter. Then switch on headlights and observe. Should be "normal" (settling needle at middle or slight charge), then when headlights go on, needle should tick to discharge and creep back to middle or slight charge within a fairly short time.
That test and the other two will expose the issue more clearly.

I don't think I've ever seen a set of 6V headlights pull more than 20 amps or so, (120 Watts, not amps) even on high beam. With a 30 amp generator, almost all the gen output will be consumed by the headlights and ignition, leaving very little capacity left over to recharge the battery. You should see the ammeter deflect very slightly to the "charge" side at highway speed with the high beam headlight on.
Jerry

You are right Jerry. I did get mixed up. Hope it's not terminal.
Was thinking 12V/100 watts. (8.3A). thanks

Sorry Dave, was a Big Beautiful Mistake

I will need to road test it to see what happens with the amp meter. In regards to battery and corroded terminals I have a new Optima battery and new cables. Everything might be working as expected. I was in the driveway and just started the truck because it had been sitting for two weeks. When I saw the amp gauge reading I started second guessing if I really knew what an amp meter was telling me.

No need to do a road test, just pull the throttle out to speed up the engine.

Yes, do tests 1. and 2. And give us that report. You need a multimeter.
After that, if you feel like getting up to higher and variable RPM's, go for a drive.

Test 1 - 5.85 volts.
Test 2
1000 rpms -5.84
2500 rpms - 5.84

Doesn't sound good

When was the last time you adjusted your voltage regulator?

Did you run the above tests against a fully charged battery (overnight or longer on a low current battery charger)? If not, they're pretty meaningless, as the condition of the battery, not the voltage regulator or generator, controls the final voltage. The terminal voltage of a fully charged, good condition 6V battery should be 6.3V or so with engine not running. Voltage from a properly adjusted voltage regulator at cruise speed against a good battery should be 7.3-7.5 volts.
Jerry

I charged the battery all day yesterday on a trickle charge. It showed at 100%. I then started and saw the draw on the battery. I have never adjusted the voltage regulator. I didn't know it was adjustable. It is new and I did polorize it. Could running it for about 10 minutes and turning on the headlights have drained it from a full charge down to 5.85v. I am putting the charger back on to make sure it is fully charged.

There are two kinds of voltage regulator- - - -"Delco-Remy" and "WRONG!" I'd rather have a good condition, properly adjusted 70 year old Delco than a wheelbarrow full of offshore made junk ones. Their failure rate, right out of the box, is somewhere around 50%.

www.ebay.com/itm/157140205091?

Try connecting a jumper wire from the regulator "F" terminal to ground, and raise the RPM slightly. That should put the generator into full output and raise the voltage at the "ARM" terminal to 7+ volts. If the cutout relay is working properly, the voltage at the battery posts should also rise noticeably. Don't rev the engine much above a fast idle, as that will overload the generator.

Jerry

The voltage regulator I installed is NOS. The box was falling apart and it is clearly a NOS regulator. Not a new offshore aftermarket. I will test the regulator output

Okay. Issue resolved. Thanks everyone for your input. I adjusted the regulator by bend the tension spring arm. Current output at battery post -
600 rpms - 6.2 to 6.5 volts
2500 rpms 7.35 volts
600 rpms with headlights on - 3 - 5 amps draw to negative side on amp meter. Any acceleration moves the amp meter needle to 3-5 amps positive side. Volts at battery 600 rpms lights on 5.8 volts
2500 rpm with headlights on 6.8 to 7.2 volts

Try cleaning the points by scrubbing them with a piece of index card, or a clean business card (NOT a file or sandpaper!) The points behind the ARM and FLD terminals are pure silver, and they can be scratched easily. They have a slight wiping action as they operate to be somewhat self cleaning, and even tiny scratches will make them stick. If you test the circuit between the FLD terminal and the regulator base with an ohmmeter with all the wires disconnected, there should be almost zero resistance. Opening either one of the spring-closed points with the ohmmeter connected will result in a reading of 5-10 ohms. The point sets behind the FLD and ARM terminals are connected in series, so opening either one will reduce the generator output to almost zero. Those points vibrate several times a second in normal operation to control current and voltage. Dirty or corroded points on either set of contacts will drop the generator output to zero. The third contact set behind the BAT terminal is a cutout relay that disconnects the generator from the battery when the engine stops

EDIT: looks like you solved the problem while I was typing! Good show!
Jerry