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Old 09-25-2012, 10:40 PM   #61
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Default Re: Is There An Electrician In The House?

There is a lot of confusion here. Bad connections will not trigger high voltage output from the generator. Blowing light bulbs comes only from one cause, voltage too high. The third brush increases the charging output but you can't separate the voltage from the amperage. The only explanation is the the field is shorted internally, delivering full battery voltage to the field, triggering an ouput that is off the charts. You need new field coils or a new generator. Temporarily swap in another gen from someone else's car and watch the problem disappear.
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Old 09-25-2012, 11:00 PM   #62
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Sounds like the generator is working exactly as it should considering the voltage drop between the generator and the battery through the cutout, wiring, terminals, etc. it's behaving precisely as expected. The cutout should not have more than 0.1 volts of drop through it under load, and 0 volts drop with little or no load. Sounds like resistance in the cutout or the terminals or cables between the generator and the battery.

One way to "fix" this is to switch to a 6VDC positive ground alternator. It isn't exactly a fix, but it will mask all the symtoms enough that you could live with them happily ever after.
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Old 09-26-2012, 12:39 AM   #63
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An interesting conversation and I only scanned the pages.
If the cut-out (reverse current relay) is solid state (diode) I would expect a .7v drop.
Batteries are like large condensers. Battery physics dictate some terms. I would expect a good 6v battery to draw a very lot of current above 7.5v. A bad battery may go to 9v on little current. if you put a line charger on a battery and it draws little current and goes to 18V (12v battery) the battery is suspect as a 6v would be..
You can run lights at 9.2/9.3V but above that you will blow them out
To achieve those voltages as mentioned the generator will not be seeing the battery.
Also and I doubt it given the info provided something to consider, if the generator is negative ground it will be in series with the battery. Yikes.
Lastly, wiring (I own an electrical shop but don't do wiring) too much information will make the task very hard to solve.
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Old 09-26-2012, 12:55 AM   #64
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I wanted to share a like story. My name is Mike btw.
I just brought my first A (I have a T). I put a carb on it, warped Tilly wasn't gonna cut it. Ran smooth as silk. About half way home it started to backfire mildly between shifts so I ran the mixture a little richer. No luck. By the time I got on the 45mph road I was humming along. Then Kaboom, car is barely running and on the shoulder gas running out the carb. Hit it with a wrench at the needle and seat. sat down and watched traffic. Tried to restart after a good while, nope!!

I thought about it for a while. Turned on my cowl lights, nope. Headlights nope..
Checked the fuse on the side of the starter. Popped up out of the the holder (30A SFE) It was too large and would not sit down in the ears and click in...

So here is what I think. At 45MPH the generator is going high, very high. The coil saturates and stops firing. Car floods and slows down. Generator voltage drops coil fires and all that gas lights off, kaboom.
Push the fuse down, drive homes purrs like a kitten.
Oh I had a small tour the next day. Pulled the brake light bulb out and yes indeed, black and blown out. Glad my headlights weren't on.
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Old 09-26-2012, 06:16 AM   #65
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Default Re: Is There An Electrician In The House?

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Originally Posted by tbirdtbird View Post
There is a lot of confusion here. Bad connections will not trigger high voltage output from the generator. Blowing light bulbs comes only from one cause, voltage too high. The third brush increases the charging output but you can't separate the voltage from the amperage. The only explanation is the the field is shorted internally, delivering full battery voltage to the field, triggering an ouput that is off the charts. You need new field coils or a new generator. Temporarily swap in another gen from someone else's car and watch the problem disappear.
Bad connections sure will trigger HIGH voltage. The Model A generator is unregulated and can put out up to 40 volts if it doesn't have a good connection to the 6 volt battery. This is why at least 3 of us make an electronic voltage regulator for the Model A's. Mine fits inside the generator where the adjustable brush normally fits. This keeps the output voltage regulated to a safe level.

With over 2 volts dropped in the battery cable with only 4 amps flowing, I'd suspect a poor connection. Give the cable a good tug and see if it is loose at the terminal. I've seen two cables that pulled right out of the heavy lead terminal. With the starter engaged the cable will be flowing at least 100 amps, and even with that heavy current flow it still should come nowhere close to a 2 volt drop.


Last edited by Tom Wesenberg; 09-26-2012 at 07:01 AM.
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Old 09-26-2012, 09:44 AM   #66
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With over 2 volts dropped in the battery cable with only 4 amps flowing, I'd suspect a poor connection.

That's exactly what I think it is too.
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Old 09-26-2012, 09:51 AM   #67
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Double checked battery cable and ground strap for tight connections. Cross member at ground bolt connection is free of paint or any other obstruction. Cable and strap are the new ones I just received from Snyder’s. Below readings are basically the same as they were with old cable/strap installed.

Voltage test results.

At idle 6.2 volts everywhere except coil ground side.
Amp gauge shows +2 charge.

At high idle
Starter and both sides of fuse 8.2 volts
Cutout battery terminal 8.9 volts
Cutout armature terminal 9.0 volts
Terminal box left and right posts 8.9 volts
Coil 8.9 and 6.8 volts
Amp gauge shows +2 charge

With idle still set high I turned on the lights and tested voltage again, Below readings are same with either high, low or cowl lights on.
Starter and both sides of fuse 6.8 volts
Cutout battery terminal 6.2 volts
Cutout armature terminal 6.6 volts
Terminal box left and right posts 6.2 volts
Coil 6.2 and 4.4 volts
Amp gauge shows -10 discharge.
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Old 09-26-2012, 10:01 AM   #68
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If the voltage is 6.8 volts at the starter and 6.2 at the terminal box, there is definately resistance somewhere. Either corroded wire, a bad crimp on a terminal, a bad connection, oil in a connection, something.

Do this- First, verify no resistance between the battery + terminal and the generator ground. Should be less than 0.1 ohms. If higher, then fix that. If 0.1 ohms or so, then proceed below.

Check the voltage right at the battery, directly across the two battery terminals. Start the car and set to high idle. Compare that voltage reading with the voltage right at the generator output.

Now, run a wire from the generator output to the negative battery terminal directly (bypass everything between them) and check the voltage at the battery terminals again. Should be pretty close to 7 volts. If not, bad generator. If so, bad electrical connection or corroded wire adding resistance.

Last edited by P.S.; 09-26-2012 at 10:01 AM. Reason: spelling correction
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Old 09-26-2012, 06:03 PM   #69
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The statement that the Model A gen is not regulated is not true. It is regulated by the third brush, like all the generators of its day and even many tractor generators well into the 50s and 60s. Granted it is not a very sophisticated means of regulation, but regulated nonetheless. And yes any generator without proper regulation can put out very high voltage. A shorted field will give little or no regulation. Yes the solid state regulators out there are much better. His readings do not indicated bad connections. They do indicate high voltage and blown bulbs indicate high voltage. Swap the gen. for a known good one for kicks and giggles and see what happens.

Advice by PS above is good advice. try it.
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Old 09-26-2012, 06:58 PM   #70
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Default Re: Is There An Electrician In The House?

The third brush only sets the amps and has no control over the voltage coming out of the generator. Therefore a poor connection in the charging circuit allows the generator voltage to rise to dangerous (for the lights) levels. Take any good running Model A without an EVR and lift the battery cable off while the engine is running and has the lights on and see what happens. With an EVR, it's no problem.
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Old 09-26-2012, 07:30 PM   #71
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Default Re: Is There An Electrician In The House?

Tom, or Mike, or any electrician,

It sounds like using one of those common starter-mounted fuses is a big gamble; if it comes loose or fails while you're going down the road, an unregulated generator would blow any lights you have on. What else? Burn the points? Cook the coil? Fry the generator? How would you know if you weren't using the lights?

I assume that the regulator in an alternator would offer protection--right?

Thanks!

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Old 09-26-2012, 07:48 PM   #72
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The fuse is never a bad idea. However, if running a fuse and an original sytle generator, you should modify the electrical system just a tad. I would run a wire directly from the generator to the battery with its own fuse, the run the wire from the fuse block to everything else.

If the fuse between the generator and the battery blows, you simply stop charging, and your ammeter would show that. if you blow the fuse between the battery and the car's electrical system, then everything comes to a halt, including the motor. That may sound bad, but a new fuse gets you going again and doesn;t allow the generator to run directly into your electrical system with no battery load.

Best bet of all- Run a separate fuse for individual circuits!

I decided best bet for my car was an alternator and the single fuse for all with a separate fuse for some electrical components. The planned project for this winter is to install a block under the "dash" (fuel tank) with separate fuses for individual things like lights, horn, ignition, etc.
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Old 09-26-2012, 08:18 PM   #73
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The fuse is never a bad idea. However, if running a fuse and an original sytle generator, you should modify the electrical system just a tad. I would run a wire directly from the generator to the battery with its own fuse, the run the wire from the fuse block to everything else. ....
Will the ammeter ever show "charging" with that setup?

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Old 09-26-2012, 09:08 PM   #74
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Default Re: Is There An Electrician In The House?

Your low readings ( highlited in red) on the points side of the coil are normal. As the voltage at this point is continuously alternating between 0v when the points are closed and 6v when open, when the car is running, the voltmeter will average these two voltage levels, giving you a some what lower reading than you might expect. The actual average voltage reading will depend on the dwell setting of the points.
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Old 09-26-2012, 09:49 PM   #75
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Will the ammeter ever show "charging" with that setup?

Steve
No, the ammeter is out of the circuit as described here.
Also, if the fuse blows for the generator, then it is no longer connected to the battery and will be putting out high voltage internally and burn itself out. Some of the other makes of cars had a fuse in the field of the generator to protect it from burning itself up.
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Old 09-27-2012, 12:02 AM   #76
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Default Re: Is There An Electrician In The House?

I should have been more clear... My described setup is a "get you home" setup only.

My suggested setup (ideally) is the alternator.

I was describing my own car.

Sometimes, when I'm typing a post from work, the multitasking causes confusion. My apologies!
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Old 09-27-2012, 07:16 AM   #77
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I have a Power House Generator on my "A". I bought it from Ron Rude. He included a modern cutout. I always wanted a Power House because they are a little different. I had a circuit breaker on the generator output for protection if the points stuck on the old cutout to prevent the generator from acting like a motor. I still have the circuit breaker on the Power House output. I never plan to run an alternator or switch to 12 volts. I highly recommend fuses but the stock system works fine.
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Old 09-27-2012, 08:58 AM   #78
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...The planned project for this winter is to install a block under the "dash" (fuel tank) with separate fuses for individual things like lights, horn, ignition, etc.
Here's what mine looks like--reasonably handy and out of sight. Hopefully, you can do a prettier job. I probably would go with more modern blade style fuses if I were doing it again. You can see my little schematic to remind me of what's what rolled up and tucked above the stoplight relay to the left.



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I should have been more clear... My described setup is a "get you home" setup only. ...
Thanks for the clarification.

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Old 09-27-2012, 09:04 AM   #79
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P.S. - Here are results of tests your suggested.

One multi-meter probe to + side of battery and the other probe to the generator housing (is this the ground you are referring to)? No movement of OHM meter detected.

Battery voltage pole to pole 6.2

Started car and ran at high idle. Initially, battery side cut-out started at 7.5 volts and slowly moved to 8.4 volts. The armature side of cut-out started at 7.8 and slowly moved to 8.9 volts.

Ran wire from battery side of cut-out to negative battery post. Checked voltage across battery terminals. Car running at high idle 8.4 volts. Car turned off 7 volts.
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Old 09-27-2012, 09:29 AM   #80
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This can not be such a big problem. Are you sure you have a six volt battery and not an eight volt battery. Three fill caps for a six volt. Try a different cut out, try a different generator and see what happens. Check wiring behind dash panel and quit with all of the voltage an amp readings. Take the generator and batteryto a parts store and have them test the generator and the battery.
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