Generator Over Charging Issue UPDATE

Seth Swoboda

Seth Swoboda

Well-known member
1931 Model A, stock electrical system. 6 volt, positive ground, generator. With the engine running and the spark fully advanced so that the engine is running at a fast idle, I have 17-18 volts at the generator cut out. This voltage is on the armature side and the battery side of the cut out. I turned the headlights on and checked voltage at all the light sockets. I get the same voltage. I swapped out the cut out for a Nu-Rex semiconductor style with the same problem.

Some things that come to mind:
1. Bad cut out
2. Bad ground at the generator or cut out
3. Short circuit in the generator causing resistance

Do you guys have any other ideas?
 
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Re: Generator Over Charging Issue

keep checking voltage going back to the battery---how much is it at the terminal block, how much at the starter -----the ground side can be checked too---one lead on the ground post, and other to cutout screw(or other bare spot on generator), anything over 0.5 V means bad ground
 
Re: Generator Over Charging Issue

Probably not the car's issue at all. The charging system on an A is notoriously "dirty". Meaning lots of AC riding on the DC. Most lower priced digital meters won't work. Try a good quality meter and likely your results will be much better. Even a cheaper analog meter will be less susceptible to the conditions. You can't actually have 18 volts on a 6 volt bulb and have it live to tell about it. I would put the original cutout back on and set your 3rd brush to proper charging current or better yet get a voltage regulator that replaces the cutout and looks original. Even a better option if you have the wherewithal is to get an internal regulator. I have the original cutout style regulator and it works great, got it from Mac's 3 years ago and have had no issues. Good for the battery too.
 
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Re: Generator Over Charging Issue

If you are reading a true Volage ( following the good advice given), sounds like a cutout problem and if so a generator killer. I don't think it's an AC issue as much as it's a lot of RF issues coupled with second and third harmonics...or a combination of all of the above.
 
Re: Generator Over Charging Issue

The light bulbs are all out of the car. Headlights, parking, stop and tail lights. They were all blown out. That is what led me to investigate. So they actually did not survive the high voltage.

I am using an Ideal brand voltmeter. I have an analog meter that I can use also.
 
Re: Generator Over Charging Issue

Willie Krash said:
If you are reading a true Volage ( following the good advice given), sounds like a cutout problem and if so a generator killer. I don't think it's an AC issue as much as it's a lot of RF issues coupled with second and third harmonics...or a combination of all of the above.
Click to expand...

In layman's terms please, lol :).
 
Re: Generator Over Charging Issue

Is your battery good? The generator needs the battery to act as a load to help regulate the voltage. If you over charged and cooked your battery, you will have charging / voltage regulation issues. Of course the battery may not run the starter any more if it is that bad. Check your voltage right across the battery if it is not very close to what it is other places in the car you have one or more bad connection, make sure all connections and wires are in good condition and clean, no rust, no corrosion, no paint, no oil.... One major problem area is the battery to frame ground and the frame to engine ground path, I installed a #2 copper cable from the battery / frame connection point to the bottom bolt of the starter to make sure there is a good path from the engine to the battery.
 
Re: Generator Over Charging Issue

The battery is like a big filter or condenseror if you will a tank you are filling up.. If you read high voltage on the generator side of the cutout (Reverse current relay) that means the voltage is high because it isn't connected to the battery. The battery absorbs that energy and becomes charged. If the generator doesn't see a battery it will go high Maybe as High as as 40 V +++++.
Think of it like a hose on a sprinkler and you disconnect the hose from the sprinkler without turning the water off. Water (voltage) everywhere.
Sorry if I'm inarticulate. Bottom line Battery physics determines the voltage as the generator is only current controlled. As current increases voltage is less, as it decreases voltage goes up, i.e the battery limits the voltage and the loads the car generates, contributes as well.
 
Re: Generator Over Charging Issue

Sounds like a poor connection in the path from the cutout up through the dash & on back to the battery.
Bill W.
 
Re: Generator Over Charging Issue

jmeckel said:
Is your battery good? The generator needs the battery to act as a load to help regulate the voltage. If you over charged and cooked your battery, you will have charging / voltage regulation issues. Of course the battery may not run the starter any more if it is that bad. Check your voltage right across the battery if it is not very close to what it is other places in the car you have one or more bad connection, make sure all connections and wires are in good condition and clean, no rust, no corrosion, no paint, no oil.... One major problem area is the battery to frame ground and the frame to engine ground path, I installed a #2 copper cable from the battery / frame connection point to the bottom bolt of the starter to make sure there is a good path from the engine to the battery.
Click to expand...

The battery is a 6 volt Optima. It's good. I test 6 volts at the battery and if I turn the lights on with the engine off I test 6 volts everywhere.

I'm guessing I have a bad ground issue. I will check this out. As well as checking out the cutout.
 
Re: Generator Over Charging Issue

Jump a wire across the two terminal box wing nuts, then use an analog volt meter to read the voltage. If the voltage has now dropped to just a bit above battery posts voltage, then you have found the problem in the terminal box, two short wires, or the ammeter. All must be clean and tight.

The best protection against blown bulbs is a voltage regulator to keep the voltage at a safe level, even if the battery becomes disconnected. An EVR is also good for the battery, and it reduces the drag on the V belt and motor.
 
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Re: Generator Over Charging Issue

Aha. Bulbs out makes a difference. Sounds like a wiring issue from the generator cutout to the battery. Could be a ground issue although if the starter cranks it tells you the ground is somewhat there, however sometimes the high current the starter draws will establish a path through a dirty connection where a lower current won't.
 
Re: Generator Over Charging Issue

Sounds like a bad ground to me.

With the problem happening, try taking your meter from the ground post of the battery, (Scratch it real good), and the chassis, (again scratch it real good to bgt to good metal). It should read zero on the lowest DC scale. If not you have a poor ground.
 
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Re: Generator Over Charging Issue

Have you installed a new generator recently ? It is passible the brushers are reversed in the generator, if so it will put out high voltage, moving the 3rd brush will not have any effect on the charge rate.

Ron
 
Re: Generator Over Charging Issue

I agree with eagle that it sounds like a poor connection between the cutout and starter switch. Just read the voltage at the output of the cutout, then each terminal box wing nut, then each side of the fuse (if you use one), then the stater switch.

I just edited my response above. I meant to say terminal box, not cutout.
 
Re: Generator Over Charging Issue

The generator is not new. I restored this car about 15 years ago. This evening after work I am going to check the voltage at all the places you guys have suggested and also check to make sure I have a good ground.

Thanks to all who have contributed so far. I appreciate it!
 
Re: Generator Over Charging Issue

Willie Krash said:
The battery is like a big filter or condenseror if you will a tank you are filling up.. If you read high voltage on the generator side of the cutout (Reverse current relay) that means the voltage is high because it isn't connected to the battery. The battery absorbs that energy and becomes charged. If the generator doesn't see a battery it will go high Maybe as High as as 40 V +++++.
Think of it like a hose on a sprinkler and you disconnect the hose from the sprinkler without turning the water off. Water (voltage) everywhere.
Sorry if I'm inarticulate. Bottom line Battery physics determines the voltage as the generator is only current controlled. As current increases voltage is less, as it decreases voltage goes up, i.e the battery limits the voltage and the loads the car generates, contributes as well.
Click to expand...

Willie your explanation makes senses. Thanks for the break down. You guys are all very helpful, many, many thanks.
 
Re: Generator Over Charging Issue

A quick jumper cable from the positive post to the frame/trans, will tell you if it's a bad connection where the ground cable bolts to the chassis.
Bill W.
 
Re: Generator Over Charging Issue

BILL WILLIAMSON said:
A quick jumper cable from the positive post to the frame/trans, will tell you if it's a bad connection where the ground cable bolts to the chassis.
Bill W.
Click to expand...

did you ever cut open a jumper cable and see how small the wire gauge is? they are mainly assist cables and not designed to carry full amps
son
 
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