The Stovebolt Site Forums The Shop Area The Electrical Bay Amp guage center

Got to my destination yesterday, but when I was ready to leave the battery was near dead and couldn't start the engine. I noticed driving back the amp meter stayed in the center. I previously remember it going to charge with good rps. Does the meter default to the center? Could I have some pointers to find the problem?

Check the voltage at the battery posts with the engine running at a fast idle. If the charging system is working properly it should be between 13.5 and 14.5, depending on the state of charge of the battery. Below 13 is very marginal- - - -below 12 means the generator or alternator is not charging.
Jerry

It should go to discharge if you haven't any charge going, but yes with nothing going on it should sit in the middle. Sounds like you have a little bit of charge going on but not enough to charge the battery. Could be a bad cell in the battery, or brushes in the generator getting worn or sticky, or voltage regulator sticking or not working. Not knowing what you have, its hard to tell. More info needed. New Battery? alternator or generator? Might just need to polarize the system again. Try what Jerry said first.

I bought a new battery and amp guage still holds in the middle. Guage dips to discharge when lights are on at idle. Heater fan does not cause amp to discharge however. New battery holding at 14 after a drive. Polarized generator. Is it possible I switched wires on reinstallation?
I should mention all this started after I took the generator in to rebuild shop to have different pulley installed. Guy took it apart and said it was dry and put on a plastic bushing I believe. I added oil to rear cup when I got home. When driving where should guage be, middle or on the charge side? I appreciate the assistance.

What is the voltage at the battery posts with the engine running? Ignore the ammeter for now- - - -the needle deflection changes according to the state of charge of the battery- - - -right after startup it will deflect toward the + side, and move back to center as the battery recharges. The only time it should go (-) is if the engine isn't running and the headlights are on, or if the load on the electrical system exceeds the generator output, like maybe high beam headlights, heater blower, and electric wipers on all at once. Check the voltage- - - -it should be 13 to 14.5 at fast idle.
Jerry

The battery stays at 14 volts when engine is running, fast or slow idle. A new battery. The only time the needle moves from center is when lights are turned on, and then just 1/8 towards D.

A dash ammeter is about as accurate as a gypsy fortune teller. Chances are the charging system is working right if the voltage is good. Does the ammeter needle return to center with the engine off and the lights out?

It always stays on the center on or off, except when lights are turned on and the only reason i know it's still working somewhat. My hunch is I miswired something if it shows a discharge but not a charge. Doesn't help that the wiring is a rats nest.

Sounds like you wired the ammeter on the hot wire to the light switch. I prefer voltmeters, much more informative IMHO.

SimS

The connection from the charging system to the ammeter is on the wrong side. The only wire that attaches to the upstream side of the ammeter is the one to the battery cable connection at the starter. Everything else- - - -ignition switch, light switch, fuse block, and charging system wiring needs to attach to the other side. That way, ALL the current passes through the ammeter, charge and discharge.
Jerry

That's what it was Jerry. I turned on lights & fan and it went to charge. Electrical was never my strong suit, plus I need a new wire harness. I certainly owe you a beer if we ever meet.

So I jumped the gun. Needle goes to C with engine on or off. Needle jumps to charge on start up. That's what got me smiling. Shouldn't accessories show discharge?

Not if the engine is running and the charging system is operating properly. If the engine is not running, then yes it should show discharge. 🛠

If it's wired correctly, "engine off/lights on" should show a discharge. Ditto for any other accessory in use with the charging system not operating, like ignition switch, brake lights, cigar lighter, etc. After startup, there should be a big deflection of the ammeter needle in the "charge" direction which gradually tapers off as the battery recovers its charge. Unless you have a bunch of accessories on all at once, the needle should not move toward "discharge" at any speed above idle.

Think of the battery as a bucket full of water. If you start punching holes in the bucket, the water level will drop, right? Now turn on a garden hose and start refilling the bucket. As long as the incoming water meets or exceeds the leakage, the water level will stay constant, or rise. If you open the hose nozzle fully, the bucket refills quickly, and would overflow if the flow isn't reduced. That's the function of the voltage regulator- - - -matching the flow of current from the generator or alternator to the load, with a little current left over to recharge the battery. As long as the charging system has enough current capacity, the light/accessory/ignition load gets met first, and whatever capacity is left over is used to refill the "bucket" (battery). The ammeter shows which direction the current is flowing- - - -in or out of the battery.
Jerry

So it's definitely wired wrong. Showing high discharge at high RPMs and slight charge with engine off and lights on. When I start the engine it briefly jumps towards the charge direction. If I reverse the wires again that's when needle stays in the middle of the guage. I'll look at it again.

Ok, I've got s red and black wire going to the ammeter. Always thought it was amp meter. Anyway there are four posts to it. Can anyone tell me what wire goes to what post?

Two of those posts are probably attaching screws that hold it to the dash. There should be only two insulated posts with wires attached to them. The one toward the passenger's side of the vehicle is most likely the one that should have only one heavy wire (10 gauge or larger)- - - -which goes to the battery cable terminal at the starter. ALL other wires should attach to the other terminal. Those will be the voltage source for the ignition switch, the headlight switch, the fuse block, and the wire going to the BAT terminal of the voltage regulator. Some ammeters have a long stud on one side that serves as a common junction block for all those wires.

If the system is wired correctly, ALL the current coming from the battery to the vehicle electrical system has to pass through the ammeter. the charging current also passes through the ammeter, once all the current demands of the ignition, lights, and accessories are met.
Jerry

If your 58 is the same as my 56, then it is possible the extra two posts are for the “55 amp generator equipment “; as it says on my wiring diagram, and how the back of my amp gauge was built. If you look at the 2 extra posts carefully you may see that they are hard wired with the other 2 posts ( again, this is if you have the same dash as I have). It does not matter which of the two posts you use on each side, or really even if you have it wired up backwards as you discovered that the gauge just reads backwards. Concerning the accuracy of the gauge, I can only reference mine that it seems to vary a lot, and sometimes shows even a slight discharge at cruise rpm. One test I have done to see if my battery is being charged (since I do not have a volt meter on the truck) is to measure the battery voltage before start up. Then after my drive, I measure it again and it should read higher than the first measurement.
Oh, and the black wire is supposed to come from the positive battery post (or starter post) and the red from the voltage regulator.