Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 01-09-2022, 02:04 PM   #1
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Generator polarizing question

Hi all, have read many posts regarding polarizing generator but still concerned i may have been unsuccessful. Just changed my car to 12v, with NEGATIVE ground now. I have installed new wiring with fuses, new 12v bulbs, and all seems to be working beautifully. However I have NOT connected my generator yet, as I wanted to ensure proper polarity to avoid issues. I have jumpered/shorted between both contacts on my generator cut out switch (no spark observed), however when I start my car and test the gen with a multi-meter, my multi meter reads -17v between case of gen and batt terminal on regulator cut out. If I reverse my multimeter leads (now using red for positive now going to the gen case as a ground and the black from multimeter now going to bat terminal on cut out as positive) it reads +17 v on multimeter…

Have shorted the regulator multiple times with same outcome. I feel like the generator is still polarized for a positive ground system?

Am I doing the re-polarizing technique wrong?

Last edited by Leyland; 01-09-2022 at 07:58 PM.
Leyland is offline   Reply With Quote
Old 01-09-2022, 04:40 PM   #2
Bob C
Senior Member
 
Join Date: May 2010
Location: So Cal
Posts: 8,713
Default Re: Generator polarizing question

I think we need more information. What generator, later 12V or stock Model A and are you using a regulator or just a cutout.
Bob C is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 01-09-2022, 04:51 PM   #3
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

Hi Bob. The car is stock model A with original 4 cyl motor and only change is now 12v and negative ground. I haven’t re-connected the generator after doing the 12v conversion, as I wanted to verify original stock generator is polarized the correct way. When the car is running the generator is currently reading -12v on multi-meter. If I reverse multimeter leads the generator produces +12v to ground so I believe it is not polarized correctly switching from positive ground to my new negative ground installation. Stock relay cut out on stock 6v generator

Thanks
Leyland is offline   Reply With Quote
Old 01-09-2022, 05:15 PM   #4
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

Perhaps my issue might be that I have disconnected the generator from the car/battery while I am performing my testing it’s output, and “re-polarizing” my gen (gen has no power connected to it while o have been doing this). I suspect the battery power has to be connected to the “battery” side of the factory cut out relay when re-polarizing. THEN By jumping/shorting (with battery power available) across both terminals of the relay will actually do something?
Leyland is offline   Reply With Quote
Old 01-09-2022, 05:47 PM   #5
Patrick L.
Senior Member
 
Patrick L.'s Avatar
 
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
Default Re: Generator polarizing question

Attach the wiring and just jump across the cutout terminals for a nano-second. That is if your using a standard cutout.
Patrick L. is offline   Reply With Quote
Old 01-09-2022, 06:14 PM   #6
nkaminar
Senior Member
 
nkaminar's Avatar
 
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,820
Default Re: Generator polarizing question

Sponsored Links (Register now to hide all advertisements)
https://www.youtube.com/watch?v=7VI4senn3PE
__________________
A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
nkaminar is offline   Reply With Quote
Old 01-09-2022, 07:56 PM   #7
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

Thanks for all the responses, and the YouTube video! After more research I’m pretty sure my cut out relay is not stock, it is not black and it has no ford script.

I see that battery power does need to be connected to the generator (with appropriate ground for your system) when polarizing the gen. I didn’t do this as I was worried I’d cause issue to the relay. I guess without knowing any details of my relay, I will have to give it a try and see how it goes��
Leyland is offline   Reply With Quote
Old 01-09-2022, 08:20 PM   #8
nkaminar
Senior Member
 
nkaminar's Avatar
 
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,820
Default Re: Generator polarizing question

If your relay is solid state, you may have to buy one made for a 12 volt negative ground system.
__________________
A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
nkaminar is offline   Reply With Quote
Old 01-09-2022, 08:49 PM   #9
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

Quote:
Originally Posted by nkaminar View Post
If your relay is solid state, you may have to buy one made for a 12 volt negative ground system.
Thank you for that, hoping mine is typical old school coil point style and not solid state
Leyland is offline   Reply With Quote
Old 01-10-2022, 09:46 AM   #10
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,371
Default Re: Generator polarizing question

The cut out would likely do better if it uses a power diode instead of an electro-mechanical set up. When running a 3-brush, a person has to have the battery connected to get the proper operating voltage. There is no regulator unless a person has one of the modern 12-volt regulators like the Fun Products type for example but even with those, there has to be a battery in the system to prevent damage to the regulator. The field can be flashed with the cut out or regulator isolated. All a person needs it the proper residual magnetic polarity in the field pole shoes to get the genny going again.
rotorwrench is offline   Reply With Quote
Old 01-10-2022, 10:09 AM   #11
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 1,142
Default Re: Generator polarizing question

I assume you replaced the field windings with 12V ones. 6V fields will overheat at 12V. The cutout is also basically a 6V relay. I think it still works, at least for a while, but best to replace with a diode type.
Badpuppy is offline   Reply With Quote
Old 01-10-2022, 10:57 AM   #12
Patrick L.
Senior Member
 
Patrick L.'s Avatar
 
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
Default Re: Generator polarizing question

The generator doesn't care about voltage, it'll put out over 20v and be happy doing it. It does care about polarity.
If power is applied to the generator input it should motor slowly [ with belt loosened] in the proper direction and that should polarize it also.
Patrick L. is offline   Reply With Quote
Old 01-10-2022, 11:46 AM   #13
nkaminar
Senior Member
 
nkaminar's Avatar
 
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,820
Default Re: Generator polarizing question

Warning: engineering content. The field poles have a certain amount of residual magnetism. This is enough to start the generating process which then supplies the field winding and produces the required magnetic flux. If the field poles loose their residual magnetism, perhaps by sitting for a while, or are the wrong polarity, then the generator needs to be re polarized which restores the residual magnetism. In generators with an external field connection, supplied by the voltage regulator, the field is briefly connected to the battery. For a generator with a third brush the same thing can be done by putting a piece of paper between the third brush and the commutator and zapping the third brush with battery voltage. Or it can be done by using the process shown in the video in Post #6.

A word of caution: On some generators the field is shorted to ground to regulate the voltage or if there is a third brush it can be the opposite polarity of the battery (ground potential).
__________________
A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.

Last edited by nkaminar; 01-10-2022 at 12:09 PM.
nkaminar is offline   Reply With Quote
Old 01-10-2022, 03:24 PM   #14
Patrick L.
Senior Member
 
Patrick L.'s Avatar
 
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
Default Re: Generator polarizing question

Yep, video in #6 is showing the motoring of the generator as well as showing how to jump the cutout to polarize.

Some cutouts do not want to be jumped. The old electromagnetic units can be.


All this info makes this as clear as mud doesn't it.
Patrick L. is offline   Reply With Quote
Old 01-10-2022, 10:43 PM   #15
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

I removed the cut out this evening from the generator, used a piece of 14g wire on the 12v + battery post, and touched it to the generators output post momentarily (where the cut out would connect to). It sparked. Did this a few times to be sure... I re-installed the cut out unit onto the generator, started the car and like magic my multi-meter read voltage with the correct polarity for my 12v - ground system!! HOWEVER…. It read 10,20,30+ volts at the cut outs battery tab!! I connected the yellow and black generator wire, and switch wire to cut out introducing the battery and lights to the gen for a load, and it miraculously regulated voltage fluctuating between 12-14 volts!!! Not sure how the cut out knows, or can tell that my new battery is 12v? Perhaps the previous owner mistakenly installed a 12v cut out on his 6v system?
Leyland is offline   Reply With Quote
Old 01-11-2022, 09:24 AM   #16
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 1,142
Default Re: Generator polarizing question

High voltage readings with no load are to be expected. Generator should not be run very long this way or it will be damaged. The cutout is a set of contacts between the generator and battery which will read the same on either side when it is operated. It operates when generator voltage exceeds 6V.
Badpuppy is offline   Reply With Quote
Old 01-11-2022, 09:32 AM   #17
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,371
Default Re: Generator polarizing question

The cut out only cares about the amount of voltage that allows it to close the circuit on the electro-mechanical types. The diode type just allows current to pass the one direction. The generator charges only by increasing or decreasing current output on a third brush unit. Once the battery is in the circuit, it only needs to keep up with that applied voltage. With no battery to control voltage then it tries to put out the maximum output which will overheat it in short order.

The only drawback with three brush generators is the limitation on output amperage which is only enough for basic systems. If a person wants to add a bunch of accessories that draw more amperage then it would either need a 2-brush generator with a control unit or an alternator with a control unit.
rotorwrench is offline   Reply With Quote
Old 01-11-2022, 01:42 PM   #18
nkaminar
Senior Member
 
nkaminar's Avatar
 
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,820
Default Re: Generator polarizing question

Leyland, The voltage is controlled by the battery. The cutout is just a switch to disconnect the generator when the engine is stopped so that the battery does not drain trying to run the generator as a motor. The third brush controls the current, not the voltage. Set the third brush to the style of driving you do and to the season. If you do short trips or drive a lot at night you will need to set it up to maybe 10 amps at a fast idle. If you do long trips and not at night then maybe 5 or 6 amsps will do. Check the battery voltage after driving. If it falls below about 12.2 volts then you need to set the current up. If you are loosing water all the time then you need to set the current down. A hydrometer will be your friend and is was Ford used when the Model A was new. If it is a sealed battery then you will have to go by voltage. Installing a voltmeter in your car in addition to the ammeter will be a very helpful tool.
__________________
A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
nkaminar is offline   Reply With Quote
Old 01-11-2022, 10:30 PM   #19
Leyland
Junior Member
 
Leyland's Avatar
 
Join Date: Aug 2011
Location: Ontario, Canada
Posts: 24
Default Re: Generator polarizing question

Thanks so much for the support and all the great advice guiding me through this. My 12v battery is sealed, and luck would have it my plan was already to install a 12v accessory plug with digital voltmeter as I had intended to monitor the system for my own knowledge. And to charge my (and wife’s) phones! I knew about the ability to adjust the 3rd brush, but hadn’t got that far yet. Perfect advice and references, this definitely helps to understand desired setting for output
Leyland is offline   Reply With Quote
Old 01-12-2022, 09:44 AM   #20
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 1,142
Default Re: Generator polarizing question

We won't tell those guys that the battery doesn't "control" anything, although it appears to - it's simply a reservoir. But that's somewhat beside the point.

It's good you have a VM to monitor the battery. Normal resting charge should be near 12.6V and charging voltage should be anything above that, up to 15.5V or so. Above 15.8 the battery hydrates, and becomes damaged. Experience will tell you where to set your 3rd brush for anticipated driving conditions.
Badpuppy is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 09:15 AM.