The Stovebolt Site Forums The Shop Area The Electrical Bay Ammeter reading full charge

Hello Folks.....my ammeter is reading full + as soon as I start the engine. The battery is in good condition so I'm sure it isn't calling for charge from the Regulator. I've read thru MANY posts here and the problems stated always seems to be NO charge situation. I've checked the generator function and it is normal ie. voltage gradually increases with F terminal grounded. I've swapped regulators with no change in symptoms. Soooooo....can anyone suggest possible causes of full + ammeter reading ? ps. this is a 12V delco system on a 235.
pps..... regulator adjustment does indeed seem like rocket science.

First thought off of the top of my head. The wires going to the ammeter have been switched.
The needle should be going negative (discharge), during starting.

If the needle is going full positive (charge) all the time, while the engine running, then this is a different symptom.

The wiring is all correct. Everything was working properly until yesterday.

Is the battery new? Has it been tested to see if there are open or failing cells?

I guess you missed this thread: https://www.stovebolt.com/ubbthread...e-voltage-regulator-hot.html#Post1401907

Download the PDF file. See if it helps.

......the battery is 6 months old. It retains it's voltage at about 12.6 volts. and has lots of cranking power. ie it acts like a normal functional battery.

If you went to 12V, you should also go alternator. Internally regulated Delco 10si. 3 wire style. Easy and cheap. Scrap all the wires and VR/Gen troubles. PM for details.

First thing to do is put a voltmeter on the bat to see what the voltage is while the engine is running. If it is about 13.8 to 14.5 the system is ok & you probably have a problem with the ammeter like the shunt is partially open. If the voltage runs up higher than that you have a defective regulator. The points on the voltage section may be stuck closed.

George

Good to hear. That leads me to wonder about the voltage regulator. Generally my experience has been when this happens it is either the battery (first) or the regulator (second). But for something completely different (if this only just started happening), check all the wires at your horn relay, your horn button, your horn...everywhere in that particular part of the electric world. This happened to me once about 50 years ago and as I recall I finally found it in a loose or broken wire/connection there.

BARTAMOS......naw, I kinda like the generator / regulator. Have you been to an auto electric shop lately and seen the pile of scrap alternators waiting for diodes ?

WRENCHBENDER...battery voltage with engine running is 13.9. I opened the ammeter. There is no shunt in there, just a brass bus bar. Nothing to break.

JON G..... I pulled out all the fuses to isolate other electrical stuff. With all the fuses out, the ammeter was still full +. I'll keep poking around in the un-fused areas.

If the original wiring harness is in use, the horn wiring is in that charging circuit. There isn't a horn fuse in the original wiring circuit and if you added one later, please check the wiring at the horn relay. The more I've thought about it, the more certain I am that was where the problem was. The problem will be an open circuit, so removing a fuse won't tell you anything...

No I haven't seen a rebuild shop in 40 years. I buy rebuilt AC Delco alternators from Flaps or Amazon that last a real long time. $50. The solid state, brushless alternators are way more reliable and cheaper that what you have. I'm guessing if there was a shop anywhere near me, they would charge more than $50.

I agree that if you kinda like the old stuff, it's your choice. But "the pile of scrap alternators waiting for diodes" does not exist. There's not many repair shops left. I am not going to China anytime soon. Folks trying to figure out how to fix a problem like yours with gens and VR's do exist. The Stovebolt archives on those troubles are voluminous. There is no argument that the solid state, "brushless alternators" are way more reliable and less complicated than what you have. Again, your reason is your reason. Probably just for nostalgia/purity. For me that is taking it too far. Reliability and availability on the road are superior.

Just the voltage regulator for a 12V is $80.

Can we hold the generator versus alternator debate until the original problem is figured out?
Thanks.

Yes, I am not going to debate it, just offer the alternative. The shops full of scrap alternators needed a comment, that's all. I have NO argument for folks wanting to stay true to their originality or enjoy working on the components.

I advise 47 chev that when Jerry tunes in, to follow his instructions and tests exactly. He will help you find the problem.

Or he can read the bulletin and follow the tests suggested there.

Update.....

I disconnected all the auxiliary wires from the ammeter, leaving only the wire from the regulator and the wire to the battery. Isolating the charging circuit to only the battery. And as Jon G said, the horn circuit is not fused so if there's a short in the horn cct, it may take some wiring with it.

I started the engine and still full + on the ammeter, so it had to be either the regulator or battery. Since I'm not smart enough to adjust the regulator I thought I'd check the battery more closely. Remembering Jon G's original comment: " Generally, my experience has been when this happens it's either the battery (first) or the regulator (second) " Words to live by.

I originally thought the battery was fine because it's only 6 months old and had a voltage of 12.6V and engine cranking was normal. This engine starts instantly so it doesn't put much load on the battery. I attached a battery charger to the battery and it showed a charge current of 6 amps. Goes to show, yet again, it's not always wise to check a battery with only a volt meter.

I'll take the battery to a shop tomorrow for a load and maybe buy another one. In any case, the ammeter /regulator / generator were working 'zactly as designed.

Thanks to all for your assistance to fix a problem that didn't exist.

Good luck with the shop and thanks for keeping us informed.

Not sure what exactly you mean by "12V delco system on a 235" but I will assume:
1. You have done a 12V swap. Correctly. Battery, coil, VR, gen..... all 12V. Ballast Resistor and etc. or you swapped a 55.2 or newer motor.
2. You have one of those "special" 12V generators.
3. You checked battery voltage motor running (gen output) and motor at rest.
4. We are talking about a truck.

Since motor starts fine under a 250-450 Amp load. Since battery shows 12.6V. Since battery stays charged....... Nothing wrong with battery.
The 12V battery charger may be trying to take it to 14V+.
The truck Ammeter is reading current, as you know.

I suspect:
1. Bad ammeter
2. Bad VR
3. Bad Generator unless it shows 13-14V motor running
4. Bad wiring/miswire
5. 12V gen is putting out more than old ammeter limit. 1947 generator was about 35 amps max.
6. Possibly some kind of polarization problem

To avoid the usual fire hydrant watering contest this discussion triggers, please send me a PM. There are a few facts about your battery you'll need to understand before you get into trying to do any more testing. It's entirely possible the indications you're seeing are perfectly normal.
Jerry

Jerry, to refresh you memory with you and 47 chev............ https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1305334/1.html