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-   -   3 brush generator ???? (https://www.fordbarn.com/forum/showthread.php?t=269497)

TJP 09-15-2019 02:41 PM

3 brush generator ????
 

2 Attachment(s)
I have a few questions that I hope don't seem to ignorant :D
I have a 39 Standard with a 3 brush generator. It is only putting out about 6.2 V to the battery. I read up and tried adjusting the third brush both directions with virtually no change.

Some have suggested to"Full field" the generator by jumpering the two terminals on the cutout momentarily to see if the output increases.

This got me to wondering if it was hooked up correctly to begin with.

The cutout terminal marked "A" has a multi stranded wire from the generator hooked up to it that I assume is from one of the brushes.

There is a second wire from the generator that is a solid strand and is attached to the base of the cutout.

On the other side of the cutout terminal "B" goes back to the battery.

So the question is which of the two wires should be jumpered to full field the generator.
I've attached a couple of pic's :)

Thanks in advance
TJP

flatheadmurre 09-15-2019 03:10 PM

Re: 3 brush generator ????
 

You canīt "full-field" a 3 brush generator since one end of the field is the one bolted to ground by the cutout and the other end is at the movable third brush.
Start by checking if the cutout is working...have someone rev up the car while you jumper the in and out of the cutout...if it starts charging then cutout needs attention...otherwise generator is prime suspect.

Kurt in NJ 09-15-2019 03:45 PM

Re: 3 brush generator ????
 

the wire that is attached to the cutout mounting screw is in essence "full fielding" it, that wire was intended for use with the oval cutout that has a voltage regulator in it.
if your battery is low on charge the charging voltage can be low, you also have to measure the amps being charged

is it a normal original relay type cutout, a diode type cutout or a fun projects regulator type of cutout ??

TJP 09-15-2019 04:27 PM

Re: 3 brush generator ????
 

I do not know the type or source of the cutout. it belongs to a friend who recently acquired it and I am trying help him out.
I suggested a small blockk chevy swap :eek: but he wasn't going for that LOL

So in summary, at about 1500 or so RPM,

If I jumper the in and out on the cutout, (marked A+B), and while doing so leave the other (field ?) wire grounded to the generator,

The charging rate and voltage should increase if the generator is OK correct ??

And if it does increase then the cutout is likely at fault, Correct again ???

Thanks a bunch :)

Kurt in NJ 09-15-2019 04:45 PM

Re: 3 brush generator ????
 

with the 3 brush the amps are set by the 3rd brush, the voltage is set by the battery and it's willingness to accept charge, if the battery is low on charge the charging voltage will be lower
what is the voltage on each side of the cutout, a diode cutout will have a .5 volt drop on the "B"side ----if you put in a 8 volt battery the generator will just make more voltage

if you have a fun projects regulator jumping it can fry it, if it is original relay type it can be jumped, diode type can be jumped too

if the field ground wire is disconnected the generator should stop charging

if the battery is disconnected from the generator it can easily make over 40 volts---till it has meltdown

TJP 09-15-2019 05:06 PM

Re: 3 brush generator ????
 

Quote:

Originally Posted by Kurt in NJ (Post 1799319)
the wire that is attached to the cutout mounting screw is in essence "full fielding" it, that wire was intended for use with the oval cutout that has a voltage regulator in it.?

Is the existing round regulator compatible with round regulator pictured in the previous post ?? :confused:

TJP 09-15-2019 05:33 PM

Re: 3 brush generator ????
 

Quote:

Originally Posted by Kurt in NJ (Post 1799335)
with the 3 brush the amps are set by the 3rd brush, the voltage is set by the battery and it's willingness to accept charge, if the battery is low on charge the charging voltage will be lower

Sorry to be a nuisance but I am trying to wrap my head around how this system works.

Based on the above quote, are you saying a bad battery will limit the systems ability to produce more current /voltage ??
Meaning if one moves the 3rd brush to produce more current it will only do so if the battery is capable of accepting the current and thereby raising the voltage.

:confused::confused::confused:

Kurt in NJ 09-15-2019 05:34 PM

Re: 3 brush generator ????
 

The Ford one that includes a regulator is oval,
Is the round "cutout" you have original or reproduction, --- perhaps if you take it off and post a picture of the bottom

Kurt in NJ 09-15-2019 05:46 PM

Re: 3 brush generator ????
 

With the 3 brush stock generator/ cutout the charging voltage will be whatever voltage the battery ends up at for the amperage the generator is charging
A reley cutout turns "on" at the voltage it is set at
A diode cutout turns"on" whenever the generator voltage is about 1/2 volt more than the battery
I have never gotten a good explanation about how the "fun projects "regulator works---- I think it just shunts the excess to ground, given how it is connected

rotorwrench 09-15-2019 06:21 PM

Re: 3 brush generator ????
 

A person has to be aware of the electrical theory behind the early auto generators used by Ford. They used the most simple design that was available. The field design is such that it will produce a voltage consistent with the needs of the battery.

The cut out it there to keep the generator from motoring after the engine is shut down. It is brought on line by the power developed from the residual magnetism in the field pole shoes when the engine comes to life and starts turning it. This is where polarization of the field shoes is important.

The third brush is the current limiter in the system and it the only adjustment that can be made for the charging process. A good quality amp meter is required when adjusting the third brush per the basic adjustment procedures that Ford used. I don't think I would trust the dash gauge to make the adjustments. Originals are trustworthy if they still function normally but I would still use a separate meter.

The 3-brush units are limited on how much amperage they will put out and are taxed when driving the car a lot at night with the lights on. This is why they finally went to a more modern 2-brush design in 1939 but they had to have a voltage controller box that had the cut out, a voltage regulator pole, and a current limiter pole in order to function and be able to put out 30 to 35 amps. Not all 39 models were so equipped since it was a change over year. Deluxe models would be more likely to have the 2-brush generator with the 3 pole voltage regulator.

There are more than a few different cut out looking devices available and some have voltage regulators (Fun Projects is one). The oval shaped units are hard to find in good condition since they were relatively short lived.

If it won't generate an amperage then something is wrong with it. It could need cleaning, lubrication, & new brushes but then it could have a damaged field or armature too.

TJP 09-15-2019 06:22 PM

Re: 3 brush generator ????
 

Thank you for your patience, I'll probably be back tomorrow with more questions :(

koates 09-15-2019 09:11 PM

Re: 3 brush generator ????
 

All the above answers are good but possibly to complicated for you to workout why the generator is not charging. Do this test, disconnect both wires off the cutout terminals and leave them free. Start the engine and let idle. Connect the two wires together, you may get a small spark here. Rev the engine up a bit and note if the ammeter is charging or not. If not charging then the generator is most likely at fault. Make sure you disconnect the two cut out wires apart from each other after the test. I suggest that if you know nothing about these generators then you take it to an auto electrician for testing or repair. Regards, Kevin.

TJP 09-16-2019 06:20 PM

Re: 3 brush generator ????
 

Today discovered that the generator was actually putting 7.3 V into the cutout yet only 6.2 was coming out. I proceeded to remove the top of the cutout and found it was a solid state type with a circuit board, capacitors etc. So I am assuming the issue is with the cutout correct ??

I wish i had a better grasp of how the system works. I think I understand the 3rd brush adjustment but the cutout is what's confusing me
thanks
TJP

JSeery 09-16-2019 06:23 PM

Re: 3 brush generator ????
 

The original out-cut is an on/off switch, it cuts the generator in at a given rpm and out of the circuit when the engine is turned off. Sounds like what you have is a regulator inside a cut-out case.

"In its simplicity a cut-out is a magnetically controlled switch that provides a path for current flow from the generator to the battery. The cutout permits charging of the battery when the engine is running and prevents the battery from discharging when not."

koates 09-16-2019 06:57 PM

Re: 3 brush generator ????
 

For your information, when testing charging voltage on a generator system the engine RPM needs to be above idle speed. Generators do not charge at idle speed as alternators do. Regards, Kevin.

Bob C 09-16-2019 09:12 PM

Re: 3 brush generator ????
 

Sounds like you have a Fun Projects voltage regulator.
http://www.funprojects.com/products/10505v.aspx


Bob

rotorwrench 09-17-2019 12:57 PM

Re: 3 brush generator ????
 

I'd say Bob C is correct. The Fun Projects set up was designed by John Regan who started Fun Projects. The little regulator basically regulates the needed current to the field. As the battery gets closer to fully charged, the current to the field is reduced so the current output is reduced as well. When the system is taxed by turning on the headlamps, more current is required so it puts more into the field. With a "GOOD" battery, the system should charge it back up to a point that all the draw necessary is to keep the ignition system running which is only around 4 or 5 amps which will be shared by the battery. In any case. it shouldn't have to put out any more than 14 to 15 amps which is about the max system capacity anyway. If the thing goes over 15 amps due to a short in the system or the battery, the Fun Projects voltage regular can fry itself. It wouldn't do the generator any good either.

31Abone 09-17-2019 04:34 PM

Re: 3 brush generator ????
 

Just a note on 3rd brush generators...never run one with wires unhooked it will burn out the gen fast....put terminal to ground if nothing else...had a 31 Nash running one time with lights on and I was fooling with battery cable which came loose ..burned all light bulbs out ..nice trick huh....so I measured voltage without being hooked to bat ..16 to 18 volts on a 6 volt system...so battery does indeed control voltage in a 3rd brush set up ..

Kerk 09-17-2019 04:55 PM

Re: 3 brush generator ????
 

The original cut out is just what it says ! When it is not charging the points are open and closed when it is charging.. IF the points STICK and you shut the engine off the Amp meter can burn out. It happened to me on 2 different times 1 first in 1953 or 54 with my 1st 32 and a few years ago with my restored 32.. Ran Fun Spot after that with no problems JME

TJP 09-18-2019 10:35 AM

Re: 3 brush generator ????
 

Quote:

Originally Posted by TJP (Post 1799780)
Today discovered that the generator was actually putting 7.3 V into the cutout yet only 6.2 was coming out. I proceeded to remove the top of the cutout and found it was a solid state type with a circuit board, capacitors etc. So I am assuming the issue is with the cutout correct ??

I wish i had a better grasp of how the system works. I think I understand the 3rd brush adjustment but the cutout is what's confusing me
thanks
TJP

Still a bit confused here. Assuming I Have the fun projects regulator, and referring to the above quote, If the generator is putting 7.3 v into the regulator should I not be seeing that 7.3 volts or so on the output side as well ?
I'm assuming the battery voltage should be at 6.9 to 7.1 with the engine running at a high idle. and maybe that is where my confusion is Sorry to be such a pest but just trying to make sure things are correct.
TJP


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