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Old 06-25-2020, 10:42 PM   #1
JoeCB
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Default Generator voltage high ?

With all the discussions of generator cut -out testing prompted me to take a look at my 31'. I have not been having any problems other that occasionally burning out a stop light bulb or two. So I checked the voltage output , engine at a fast idle and I'm seeing 10 volts. This seems high for a stock 6 volt system. So what's going on here? What should the output voltage be?

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Old 06-25-2020, 10:58 PM   #2
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Default Re: Generator voltage high ?

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Old 06-25-2020, 10:59 PM   #3
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Default Re: Generator voltage high ?

To start with, possible poor ground on the battery ground cable. Try cleaning both ends of the cable and at the frame where the cable attaches.
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Old 06-26-2020, 06:20 AM   #4
old31
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Default Re: Generator voltage high ?

10 amps is too high.

Without the headlights being on you should have about 2-4 amps. If you dont drive with your headlights on you need to turn down the generators 3rd arm so the voltage is lower.
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Old 06-26-2020, 07:33 AM   #5
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Default Re: Generator voltage high ?

Quote:
Originally Posted by old31 View Post
10 amps is too high.

Without the headlights being on you should have about 2-4 amps. If you dont drive with your headlights on you need to turn down the generators 3rd arm so the voltage is lower.



You may have mis-read? Poster indicated 10 volts, not 10 amps.
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Old 06-26-2020, 08:32 AM   #6
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Default Re: Generator voltage high ?

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Being as the battery that is used controls the voltage , I've got to wonder if Joe meant amps . Raise the adjustable brush in the generator to reduce amperage out put . Just a thought .
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Old 06-26-2020, 08:48 AM   #7
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Default Re: Generator voltage high ?

Not amps, defiantly 10 VOLTS. Getting 10 volts reading from the generator and at the junction box. I'm using a high quality accurate VOM.
Now please understand that this car has been in my ownership for over 50 years, nothing on the electrical system has been changed or replaced in all that time ( except addition of the 20 amp fuse block) , so this high voltage condition must have always been there. Other that occasionally burning a tail light bulb , no problems. Batteries last years, no problem.
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Old 06-26-2020, 09:06 AM   #8
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Default Re: Generator voltage high ?

You only burn out tail lights? Not headlights? A 6V system should charge around 7.2V. Do you have a ground going to the engine/transmission? I agree it's probably a weak ground.
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Old 06-26-2020, 09:15 AM   #9
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Default Re: Generator voltage high ?

Ground connections deteriorate over time. Grounding problems usually creep up on you.
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Old 06-26-2020, 11:29 AM   #10
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Default Re: Generator voltage high ?

Thanks guys, I will go and check the "old" ground connection to the frame and add a ground direct to the engine.
I'll report back on results

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Old 06-26-2020, 11:38 AM   #11
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Default Re: Generator voltage high ?

Good info above regarding the ground[s].

Just for the heck of it, what is your charge rate [amp reading] ?
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Old 06-26-2020, 12:15 PM   #12
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Default Re: Generator voltage high ?

FWIW:

Before you spend too much time on this I would try an old Analog meter.


I still have a Simpson Model 260 I got in late 50s.


In the late 70's every time I tried the Company Fluke Model 8020A ( late 70's meter) on a running engine it did not work well ... too much electrical noise from Model A ignition or generator.


I have not tried the Fluke 77 to see if they shielded that one better.

I might try that this weekend!

Last edited by Benson; 06-26-2020 at 04:11 PM.
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Old 06-26-2020, 01:05 PM   #13
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Default Re: Generator voltage high ?

I am using an "old" high quality analog meter... the only thing I trust. As for charge rate, I'm at 10 amp maximum, and have been that way for years, seeing no battery problems. However , understand that I do not normally do long daytime drives.

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Old 06-26-2020, 02:47 PM   #14
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Default Re: Generator voltage high ?

Quote:
Originally Posted by JoeCB View Post
I am using an "old" high quality analog meter... the only thing I trust. As for charge rate, I'm at 10 amp maximum, and have been that way for years, seeing no battery problems. However , understand that I do not normally do long daytime drives.

Joe B
Ok Joe,

I sent that out just in case ...

Last edited by Benson; 06-28-2020 at 05:35 AM.
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Old 06-26-2020, 04:05 PM   #15
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Default Re: Generator voltage high ?

Actually the 10 amps will work if you use the Model A Voltage regulator that every car has as standard equipment!

Run with headlights turned on most of the time in daytime.

When battery was low turn off lights in day time.

This does not work if you have sealed beams though!



This was Very much like the Honda 150 which had a switch on handle bar to turn on lights.

Three positions:

1. Lights ON with Magneto charging for night.

2. Lights OFF with magneto off also, for day time so would not over-charge battery.

3. Lights OFF with magneto ON to charge a low battery during daytime.

All you had to do was remember to charge battery if it cranked slowly on start up.

Last edited by Benson; 06-26-2020 at 04:13 PM.
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Old 06-27-2020, 08:24 AM   #16
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Default Re: Generator voltage high ?

Generators run high voltage when there is a bad connection someplace in the charge circuit, normally ground but it also can be on the negative side also! Check all connections from gen to battery and negative post on battery!
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Old 06-27-2020, 09:30 AM   #17
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Default Re: Generator voltage high ?

Ford rated the stock 2-pole generator at 7.9V maximum.
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Old 06-27-2020, 09:42 AM   #18
rotorwrench
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Default Re: Generator voltage high ?

The battery controls the voltage in the system on a 3-brush. A model A generator will put out 12-volts if you use a 12-volt battery in the system. This is what makes it important that the battery be in good condition and the connections to it be clean and tight at every applicable location. You might want to get he battery load tested. It may have a problem developing if all the connections are good to go.

The generator may have brush wear or armature problems lurking in there.


2-Brush generators were actually regulated so they were set at 7.1 to 7.2-volts. It doesn't work that way with 3-brush generators. Voltage can be lower or higher than that depending on where the third brush is set.
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Old 06-27-2020, 10:58 AM   #19
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Default Re: Generator voltage high ?

The Fun Projects can style voltage regulator takes the place of the cut out and regulates the output of the model A generator similar to modern vehicles . This wonderful little device has been on the market for many years and has worked well for me .
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Old 06-28-2020, 02:01 PM   #20
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Default Re: Generator voltage high ?

OK fellows, I'm reporting back after freshening up the battery ground connection and installing a ground direct to the engine. Still getting 10 volts at the generator ( 3 brush, original) , however, strange I see 8 volts when I test the at the terminal block and at the fuse block at the starter switch. This all with the engine at a fast idle ( shows 10 amps charging). The battery is 4 years old but seems very good, cranks normally.
I can't help but think that this is all the way it's been for years, no apparent problems.
At this point I'm thinking … If it ain't broke , don't fix it !

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