The Stovebolt Site Forums The Shop Area The Electrical Bay Can you confirm the diagnosis?

59 1/2 Ton 3100 with 235 6. New stock harness and voltage regulator with rebuilt Jim Carter supplied Generator. I have had an interesting deal with my ammeter grounding out, melting a wire from the starter etc. I got all that straightened out and placed the new ammeter in and noticed the ammeter is still not showing charging but does show discharge with lights on. I see from the archives here that a couple of tests can be used to troubleshoot the charging system.

I pulled the field wire from the regulator and grounded it and got no charge when revved up. I next pulled the ground battery cable after it was running a while and it died right away. All things being equal I have a bad generator correct? Carter they will send me a new rebuilt.

IF the generator is polarized properly, grounding the field terminal will put it into full output. Here's the test sequence:

1. Disconnect the "Armature" wire from the voltage regulator, and momentarily flash it to the "battery" terminal, maybe 1/2 second or less. You should get a pretty strong arc.

2. Disconnect both Armature and Field leads at the regulator, and start the engine. Check voltage at the Arm. terminal of the generator. There should be bewtween 1/2 and 1 volt present, and it should not change appreciably if the engine is revved up. This is called "residual" voltage. It indicates the generator has been polarized properly. No voltage? Polarize again, and recheck.

3. Stop engine and reconnect the leads at the regulator. start engine. Armature voltage should rise to 13 volts or more, and the ammeter should indicate a charge. Not enough voltage? Ground the field wire with a jumper lead (no need to disconnect anything) Voltage should increase without limit as the engine is revved up. DON'T EVER DISCONNECT A BATTERY CABLE WITH THE ENGINE RUNNING! THIS IS NOT NEGOTIABLE! I have seen voltage spikes of over 100 volts as a cable is disconnected. Ith's not terribly damaging to a DC generator, but if there's any type of electronic device, including a digital-display radio on board, you're running a real risk of cooking the electronics with a voltage spike!
Jerry

Ralph,

I don't know if your generator would charge even using the tests you outlined above if it hadn't been polarized yet. Touching BATT to ARM momentarily should do it.

Stuart

POLORIZE THAT PUPPY.

I polarized it initially by use of a jumper wire across batt and arm with a spark showing. After I installed the new ammeter and reconnected the battery, I again polarized just in case... but I did it at the regulator. I am going to follow the above advice from Jerry on checking the generator at the arm terminal of the actual generator. I have had the truck running enough to think if it was running without a generator working I would have killed the battery. I just can not get the ammeter to move into charge and the last one did exactly the same thing. The grounding of the field terminal of the regulator did nada...... on the gauge.

By the way Jerry, I only removed the ground wire (which I clearly will not do again based on your caution) as I thought it was a good indicator of the generator working and saw it in the archives...... Did the truck stalling right away indicate it was not working besides being the wrong thing to do? You electron guys know how to keep us regular (read baffled) guys scared of the ohm-amp-current- burn you down monster...

Lastly, should I repeat polarization or is it like being kind of pregnant??


Thanks Ralph

Okay I just ran in from the garage to type this. Jerry, the test you had me run indicated 1 volt at the arm terminal of the generator with both the field and arm wires removed from the regulator. I guess it is polarized. The ammeter shows no charge when I do the rev test with the field wire jumped to ground at the regulator. Truck runs and lights are bright but I can't get a positive twitch on the ammeter. I will check for voltage across the battery as I get a second set of hands here. Meanwhile I am hoping that it is the newly rebuilt generator...two ammeters not showing charge is goofy.

Have you checked the voltage at the bat. or bat. term on the reg. with the engine reved up a bit.? Like HRL says the voltage should build up as it runs & stop about 14 volts. If it does your system is working. I think maybe you have the amp. meter hooked up wrong.

Ralph,

This statement might not apply to your '58 Apache, but on an AD ammeter, the charging system and all the loads (almost all) connect on a post that is physically behind the 'discharge' logo on the front of the gauge. The large wire going to the battery connects on the post located behind the 'charge' or + notation on the gauge.

Even if you had your gauge hooked up bass-akwards, the needle would still deflect, just incorrectly.

Stuart

If he's got the wire from the Bat. terminal on the regulator hooked to the wrong side of the ammeter, (connected on top of the wire from the starter terminal), it will charge OK, and the ammeter will never show a deflection. The Bat. wire from the regulator should attach to the same ammeter terminal as the wires from the ignition switch. There should be only one wire on the side of the ammeter where the voltage comes from the starter to the meter.
Jerry

I have the wire from the starter running to the Discharge side of the Ammeter and it is the only wire on that side of the gauge. The wire from the ignition switch along with the wire from the regulator are on the Charge side of the Ammeter.
Ralph

It sounds like you're hooked up right, so there's no reason the ammeter shouldn't deflect in both directions if it's OK internally. Is this an original-equipment ammeter, or an aftermarket item? Try this- - - - -connect a battery charger to the battery wire at the regulator with the engine off, and see if the ammeter shows a deflection in the "charge" direction. The battery charger gtound can attach anywhere, either at the battery, or any point on the engine block, etc.

Is the battery staying charged, or have you run it long enough to tell? Voltage at the battery terminals with the engine running should be above 13 volts if the charge current is getting there.
Jerry

Jerry,
That test is just what I needed. The battery charger finally made the ammeter needle move into the charge side. I called Carter and a replacement generator is on the way. It isn't doing the job as the voltage at the battery is not indicating a charge when it is running. Everything else checks OK. Thanks for the tip. The ammeter is a repro and after the first one shorting out (my fault I think with the speedo cable being unsecured) I was suspect of the import gauge. The battery charger showed the deflection to positive right away.

Ralph

Check out my article in the Tech Tips section on generators and regulators. It's possible the cutout relay on your regulator isn't closing, which will keep the armature voltage from getting from the generator to the battery. Generators do not have the one-way diodes like an alternator does, so there must be a mechanical relay to keep the battery from discharging through the generator anytime ganerator voltage drops lower than battery voltage. The cutout relay should close whenever the armature voltage rises to about 1 volt over battery voltage, and it will open anytime current tries to flow backwards through the relay.

If you've got a 12 volt system, the cutout relay closing voltage should be about 12.8 to 13 volts. You can take the cover off the regulator (carefully- - - - -don't short anything out!) and watch the points close as the generator speeds up. When the engine shuts down, or idle speed gets really low, the points should open. The other two windings under there regulate maximim current to a low battery to keep the generator from burning itself out, and max voltage against a fully charged battery. It's possible to clean regulator points with a piece of index card stock, or a business card, but NEVER USE A FILE OR SANDPAPER ON REGULATOR POINTS! They will stick together if they're roughed up.
Jerry

>>It isn't doing the job as the voltage at the battery is not indicating a charge when it is running.<<

Could you be even a little bit specific. An actual voltage reading.

My Ammeter reads "0" all the time. If it reads anything else, I know I have a problem. By anything else, I mean neg or positive.
It usually drains very little current from the battery to start the truck. That small drain is replaced very rapidly. Driving down the road, the ignition and radio draw very little current from the battery. The generator or in my case an alternator has to supply very little current to maintain the battery. That means the ammeter shows a very small or no reading. It will however, maintain 13.5 - 14.5 Volts across the battery when the engine is running and 12.5 V with the engine off. With your generator you should check the voltage at a high idle..
When an ammeter begins to show a charge above the normal reading, it is usually time to find the battery warranty and see how old the battery is. It means I have one to three weeks before the battery dies. That is why I prefer a dash ammeter as opposed to a volt meter. A volt meter on the dash will continue to show 14 V up until the time the battery has died. No warning.

The iron poles in the generator retain a residual magnetism. If the polarity of this magnetism, north - south is switched the generator will try to charge in the wrong direction. This will destroy the regulator and generator. A generator is "polarized" to correct the polarity of the magnetism in the poles. Once a generator is installed, wired properly and polarized, it does not need to be polarized again. That is unless you do something to reverse the polarity.

Richard,
I have a rebuilt generator that does not charge. My ammeter shows a fairly big deflection into discharge when I pull the lights on, and almost re-centers when I turn the lights off. However, the needle will not move a bit into the charge side of the gauge at high rev. The battery is new and shows less than 13 volts when running at rev. I am going to replace this rebuilt generator with another from the vendor. They said it occasionally happens where one is not up to the task. My experience with these ammeters is that they do show a bit of deflection both ways when used with the stock system and generator. That may be different with your alternator but usually the ammeter generator is a good sensor of charge / discharge. Ralph

Ralph, before you return that generator, check the voltage at the Armature terminal of the generator, and/or the Arm. terminal at the regulator. It's possible the generator is able to charge, but the cutout relay isn't closing for some reason. The fact that the circuit works from the regulator to the battery, and the generator's got residual voltage makes me very suspicious of the regulator itself. If you ground the field terminal and voltage increases at the Arm. Terminal, the cutout relay is the problem. No voltage rise at the Arm. terminal, then you do have generator problems.
Jerry

Ralph,

There has been lots of information on this post so I don't know if I'm flogging a dead horse. It makes sense to me to check each component individually to clear your list of probably suspects.

Have you ever disconnected the generator, attached a voltmeter to ARM and run the engine up in RPM as you touch FIELD to ground. This takes all the wiring and regulators out of the equation and tests only the generator. If this proves good, scratch it off the list and examine the wiring from generator to regulator.

When that proves to be good, move on to the next step. The test with the battery charger attached to the ammeter feed wire moved the meter which proved it works, so the next logical step would be to start at the generator and work toward that feed wire to the ammeter.

The generator is sort of a stand-alone unit. It can be tested all by itself for functionality...it works or it doesn't. Does this make any sense!

Stuart

Thanks Jerry and Stuart. As if this whole episode can not get any more goofy, I decided to actually use the OHM meter and trace wires etc. after I read Stuart's advice just to double check the brand new harness (stock).

The wires are numbered with simple instruction which are perfect for a guy like me. When I look at the wire marked FIELD (blue wire) that hooks to the generator and the opposite end (blue wire) that exits the harness next to the regulator and is marked FIELD, I get no continuity. Then when I continuity test the regulator end of the wire marked ARM with that same blue field wire from the generator harness, it shows continuity. This is with all wires off the generator and off the regulator. I start pulled the connector apart in the middle and to see what in the world, can I be this much of idiot? Oh yeah, I can..... check the easy stuff first....no metter how simple it seems... The two wires ARM and FIELD at the pre-wired round plastic connector in between the two were crossed so when it was pluged in they were opposites..... Jeeeez, I feel stupid but the upside of this adventure is I learned a lot about the Ammeter/Regulator/Generator. Just the information alone helped me start to parcel out the troubleshooting. Stuart and Jerry you are the MAN. (men) Thanks Ralph

'I love it when a plan comes together!"

If all the projects were simple, and worked perfectly, nobody would ever learn anything! Once you get the crossed-wire situation corrected, I'd suggest polarizing the generator one more time, and before you reconnect the wiring to the regulator, open the top and use a piece of clean file card paper to burnish any corrosion buildup off the points. Don't change any of the adjustments, just insert the card stock between the points and gently rub any deposits away. You'll be surprised how much dirt a clean-looking set of regulator points can give up, and how much better things will work.
Jerry