Technical Huge voltage swings

Hey guys I’m kind of stuck on what’s going on with my charging system.

I was driving one day and shut it off and when I went to restart it the battery was dead. It would not hold a charge so I replaced it.

Upon replacing it I polarized the generator and then checked with a multimeter to see that the voltage was swinging from 16V to 0V and everywhere in between.

I replaced the voltage regulator…still messed up

I ran the engine with no generator or regulator connected and it still had the voltage swings.

Checked all my grounds for continuity and everything looked good.

Pulled every fuse one at a time and ran it, no change.

I’m completely stumped and don’t really know what else to look for. Any thoughts or suggestions on what to try would be greatly appreciated. Thanks, Joe

 

Try checking it with an analog volt gauge. Sounds like you are getting false readings from your multimeter.

 

If it does the same thing with an analog meter and the generator/regulator is disconnected, then I would take a glance at the starter as I assume it is the only other item still connected to the battery.

 

Does your charging system run through the amp guage ? if so does it run through both sides as should , I would also recheck grounds, especially at the regulator

 

I tjimk it's a connection related problem. Dedicated ground from engine to chassis and battery? As others suggested, verify meter with a different one. You can just remove the ammeter by connecting the wires together for test; just put both wires on same terminal. If you disconnect the generator and regulator, then just run off battery does it still fluctuate voltage?

 

What car are you working on? Where are you connecting your voltmeter? Have you tried connecting the voltmeter to another vehicle to rule out a meter problem? I have a voltmeter that behaves this way when the meter battery is near dead. I don't see any other way to have a 16 volt spike with the charging system disconnected.

 

Faulty starter? Staying engaged and making voltage?

 

...or try to move to a position further away from the ignition system.
Interference from the ignition system can really mess with sensitive meters, and digital multimeters do fit that description. Letting the wires from the meter hang over some part of the ignition system while testing is a recipe for disaster - but easily done if you don't know about it.

 

If the generator is disconnected there should be no possibility of a voltage spike because there is nothing generating voltage to cause a spike. This is another of those questions that brings the bull shit artists out of the woodwork so be damned careful about reading some of he comments.

If the meter is working correctly you should just see a drain over a period of time with the generator disconnected. Meaning a 12 volt fully charged battery should show 12.5 volts and as you run the engine the voltage should continually drop and if you turn on the lights it will drop faster.

The possibility of the starter spinning and causing voltage spikes is well beyond slim and none. First you would hear it spinning and making a racket.

I would get my hands on a different test meter and preferably as BJR suggested an analog gauge rather than a digital gauge. There is something screwy with that meter.

The only generator that I have ever seen charge that high self destructed in the process and that was all due to a stuck regulator back in the 60's. It melted the solder on the armature in the process. That one just pegged the ammeter and died not long after.

 

I agree on the starter. If the overrunning clutch failed and it was being driven by the flywheel, I think the armature would explode quickly.

 

I'd consider either finding someone with a clamp on amp meter you can borrow and see what the amperage to the positive terminal of the battery is doing during these swings. Or wire in an inline amp meter on the main lead to your fuse block so you can watch it as the voltage fluctuates. If the amperage follows voltage changes, then you've got some intermittent heavy draw that could be a short, or something else.

 

I'd start cleaning connections... any and all. A poor connection can act like a capacitor and generate the spikes. Don't forget switches, try wiring around those to check.

 

Thanks for all the suggestions guys, I found an analog tester I can borrow to try. The car has a magneto so I can run it with pretty much everything disconnected except the starter.

I went over all my grounds with ohm meter and everything looks good.

Yes the Amp gauge is wired correctly also.

 

Checking connections with an ohmmeter will find a bad connection. However, it doesn't really tell you if you have a good connection. A connection can pass an ohm test and fail under load. That's because an ohm test is a static test. The only good test for connections is a voltage drop test because it is a dynamic test. You must have current flowing in order to run a voltage drop test.

I'm wondering if the magneto can be interferring with your digital meter. On the car I had that ran a mag, the complete wiring loom consisted of a wire from the mag to a kill switch and then to ground.

 

Don't quote me on this, but I believe magneto ignitions may be worse than any other type of ignition when it comes to interference that can disrupt sensitive electronics. So there's absolutely a risk of that.

 

So I have tested the car with the analog meter and the voltage is not swinging. It allowed me to see that the voltage was way high hovering over 15V. I took the cover off my “NOS” regulator and it has clearly been messed with seeing the field adjusting screw turned all the way in with the tab bent way back.
Going to find an actual NOS regulator and give it another try.
Thanks for the suggestions, Joe