The Stovebolt Site Forums The Shop Area The Electrical Bay vibrating ammeter needle

Hello Folks: I have a '47 pickup with a 235 / 12 volt upgrade....which has worked fine for many years. Recently, my ammeter gauge needle has been bouncing back and forth, more like a vibration than swinging. But still pretty large swings.
So far I have : - checked and cleaned the generator brushes and commutator
- cleaned the points on the regulator
- replaced the regulator
- cleaned all the ground points in the circuit back to bare metal
- checked all the connections for tightness in the circuit.
- checked the battery condition (good shape)
I think that only leaves the gauge itself as the problem. Can that be true ? Has anyone had this bouncing ammeter problem and solved it ?
Thanks for all your comments and ideas....as always.

Unlikely the meter would do that. Mine on my '53 bounces quite a bit... and in my case it's regulator "function" of an older regulator. When I first start and some healthy charging is needed, it's steady. After driving awhile, the current drops back, and the bouncing begins. Since even a new regulator may have sat on the shelf for a while, maybe some film on the points. Inspect and if they look pretty good, clean with a little abrasion - point file (spoon or riffler file by the Delco book) preferred, never emery cloth or sandpaper. Shouldn't have to remove material, just burnish, if that makes sense. That may do it. But another thought... have your disconnected the battery? If so, make sure that you repolarized the generator (depending on generator/regulator, that's usually just a momentary jumper between the Arm and Bat terminals). Hope this helps!

᠁᠁...thanks Dr. Doug. In my case, the needle used to be very steady but now it bounces so something (probably bad) has changed. I'll try and re-polarize the generator.

You're welcome. Another thought... risking stating the obvious. If cleaning the regulator points doesn't help, make sure the connections are all clean and tight - generator, regulator, ammeter, and ammeter to starter solenoid, battery cable and grounds. Possibly some recent corrosion or a vibration loosened connection, I suppose, since the meter used to be steady. Not sure exactly which regulator you have, since 12V converted, but the attached Delco bulletin copy dated 8-1-60 has the procedures for cleaning and adjusting the points in case you need the info.

I suppose there is some irony in all this - I should probably see why my ammeter is bouncing at low charging current, too. I assumed it was "normal operation."

Hope this helps!

Run a ground wire from the base of the regulator to the gen. There is a tapped hole in the gen. for this purpose & a hole in the side of the regulator base to put a small sheet medal screw in.
Hook a voltmeter up the system & see what happens. If originality is not all that important consider changing to an alternator.
George

Dr. Doug......thanks for the regulator tune up info. I really don't think it's the regulator 'cause I changed out the reg with no change in the ammeter issue. This morning I'll try polarizing the generator and then run a separate ground. Altho, as previously stated, I cleaned all the reg ground mounting points back to bare metal.
And noooooooooo, the bouncing ammeter isn't normal. HA, I searched "ammeter" in the forum and actually read thru ALL 40 pages of ammeter related issues. Seems like you and I are the only people caring/noticing this.

Mr. Wrenchbender᠁..I kinda like the original look of a generator. And they DO work well. I don't think the problem is with the generator or the regulator.

Never- - - - -EVER- - - -use a file or sandpaper on voltage regulator points. They contact each other with a slight wiping action, and the scratches left by a file or any sort of abrasive will cause them to stick. They are also pure silver, and very soft. Use a clean piece of stiff paper like a business card or an index card to burnish any oxidation off the points and check the setting of the point spring tension with the engine running at a fast idle and a known fully-charged battery with a specific gravity reading of at least 1.260 on all the cells. The battery terminal voltage should be at least 13.8, with a maximum voltage of 14.7. Once the metal cover is reinstalled after adjusting the voltage setting, the voltage will drop approximately 0.2 V due to better magnetic conduction of the metal cover.
JKerry

᠁᠁..latest observations: I polarized the gen and ran a separate ground as well with no difference in the ammeter readings. I wired in another ammeter in series with the dashboard meter so I could watch both needles at the same time. And both ammeters react exactly the same. Soooooo, in light of Hotrod Lincolns disparaging remarks about aftermarket regulators (and his obvious depth of knowledge) I'll try out a genuine Delco Regulator. I'm using a no name "made in USA" regulator now but still not branded Delco.

Mr Hotrod Lincoln......the generator I'm using is from a '56 Chev car. In your archives do you have a part number for the correct Delco regulator ? Ebay has lots of regulators but I'd like to get the correct one for this generator.

Your problem my well be in alternator BUT also may be in the down stream side, or load if you will. I would think that an analog, not digital, voltmeter across the output would see a fluctuation that ‘mirrors’ are the ampmeter. If down stream pulling fuses, if you have them, is an option.

᠁.tclederman᠁.thanks for those numbers. Amazing the detail GM puts down on paper.

Did you have the armature in the gen. tested on a growler?
You could have a short in the armature. With the engine running at a fast idle look in the back of the gen. & see if there is a lot of sparks. A small amount between the brushes &
commutator is normal but fire all over the place is not.

Wrenchbender᠁..no, I did not growler test the gen. I looked at the running generator in the dark and no sparking. It charges to 14.2 volts so I'm pretty sure the gen is fine.

Take the cover off the regulator, and see if the cutout relay points (the ones behind the BAT wire) are cycling on and off rapidly. That can cause the ammeter to fluctuate and sometimes it can be cured by raising the "closing voltage" by tightening the spring for those points a TINY bit. A 12V regulator should have a closing voltage of 12.75V or so.

Hotrod Lincoln....yes, looking at the schematic, chattering cutout contacts would cause this issue. So here's what I did. I put a large mirror on the front seat so I could watch the ammeter while looking at the cutout relay. I put extra pressure on the cut out contacts by holding them closed with my finger but the ammeter needle was still fluctuating a lot. Always to the charge side of the gauge.

OK- - - -next suggestion- - - -the current regulator (behind the "ARM" wire terminal) is in series with the voltage regulator winding. If it's set a little low, it can interrupt the field current and cause a fluctuation in charge current. Try increasing the spring tension on those points a little. It's beginning to sound like my "Use Delco parts" advice is going to apply in this situation. Too bad I can't drop by and tinker with that one- - - -it sounds like an interesting challenge! Be sure you've got a good ground between the regulator base and the generator housing. I like to run a wire between those two parts to assure there's not a high resistance ground path from the engine to the firewall. That can cause all sorts of oddball charging problems.
Jerry

᠁...is it possible to attach a short video of the ammeter ? I love the old chev truck 'cause I'm a techno tard.

My email is in my profile. I don't know about sharing with the whole forum, but I'd like to see it.
Jerry

I am going to call the fluctuating ammeter needle resolved. I believe the problem was the fine wire flexible conductor to one of the brushes was barely touching the gen case....close enough that engine vibration was enough to intermittently cause the wire to just touch the case (to ground) and thus cause the gen to tend go to full output towards the + side of the ammeter. Which it always did. After pushing the wire well clear of the case, the ammeter is now completely calm with a charging voltage at 13.8.

Thanks all for your thoughts

Thanks for the update, it’s appreciated.🛠

Wow! Nice find!

Folks, I’ve been struggling with my ammeter gauge needle bouncing around a lot. In reading this thread, drdoug says, “ But another thought... have your disconnected the battery? If so, make sure that you repolarized the generator.” I installed a battery cutoff switch on the positive red cable to make it a little harder for someone to make off with my truck. I have turned that switch off many many times which is effectively disconnecting the battery. Is this screwing up the polarity of the generator each time, and have I damaged the generator or regulator? I don’t know if it’s related but right now I can’t get my truck to start.

It could be the problem but you probably didn't damage anything.

My polarity became reversed once on the Cadillac and when I turned the key to "ON" ( not "Start"), the generator acted like a starter and tried to spin over the engine.

I used a pair of needle nose pliers to polarize the Genny and it worked and everything was back to normal with no apparent damage. Since then, I always polarize the genny whenever the battery is re-connected.

What do you mean that the truck won't start?

Does the engine turn over at all? Is the battery dead?

Is the battery fully charged but the engine won't turn?

Thanks for the reply. I had it running earlier today and last night. Haven’t changed a thing. I’ve checked grounds only with a multimeter to make sure they were good. Engine turns over but I’ve worn the battery down and it’s on a charger now. Lately it had been starting right up. Last night the excitement was the ammeter bouncing around during a test drive (about 5 miles), as it always seemed to do, but it was dusk and I turned on the headlights. All good, then as the ammeter was bouncing around the headlights and dash lights were oscillating between dim and on. I turned them off and came straight home. Checked the headlight grounds and they’re good. I haven’t had this truck long but it’s never run well.

Mark WH, I think you're going to have to do a top to bottom test/check/r&r on the ignition system and the electrical system in general.

You should start a new thread with all of your issues to start a diagnosis with a clean slate.

Start with your plugs/gaps and then the wires. If they are of dubious condition or unknown age, buy new ones. Check the cap and rotor. Test the coil.

Make sure the points are perfectly adjusted and I strongly suggest getting one of Jon G's 200,000 hour condensers. Many strange driveability issues stem from the horrible ignition condensers available today from parts stores.

Is your truck still a 6v? If so, make sure your starter cable is 1,0, or 00 gauge cable and that all your connections are clean and tight. How about your generator and voltage regulator? If they are of unknown provenance, I would take both of them to an electric starter/generator shop for testing.

6v systems require a fully charged battery and perfectly functioning generator and voltage regulator to operate correctly. When all three are in sync, the starter will spin the engine as fast as a 12v system.

I can’t find where to buy JonG’s condenser. Is it in the Swap Meet section of the website?

Just send him a Private Message via this site. Or, look at the 2 Sticky notes at the top of this page.

Mark, a bouncing/vibrating ammeter needle is the classic symptom of a generator that needs polarizing (as covered earlier, engine off, momentarily jumper the BAT and ARM - sometimes marked GEN - terminals at the voltage regulator). But a V/R that is failing might cause similar symptoms, as may grounding issues. I'm sure you know, but the 6V system is hyper-sensitive to connection quality - grease, paint, corrosion free and tight - which applies to all ground connections (battery to engine/body/frame and between each) as much as positive/power connections. Adding a new, separate ground wire from generator body to the V/R mount might help, as well.

The suggestion from Otto to separate the issues and systematically work through them one at a time makes sense, of course.

Hope some of this helps!

Doug