Testing a Generator

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Model T Ford Forum: Forum 2012: Testing a Generator
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Brown on Tuesday, April 24, 2012 - 12:48 am:

This may sound odd but years ago we had a belt break on our car and the generator would motor or turn from the power feeding back thru it through the regulator from the battery. If I had a T generator laying on the bench and connected the negative terminal to the housing and touched the positive terminal to the output post would the generator motor if it was any good? The cut out would be removed.
Also would 12 volts do any damage as it would be connected for a very short period of time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Tuesday, April 24, 2012 - 12:52 am:

If it does not "motor" it isn't any good.
A few seconds of !2 volts will not harm it


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Tuesday, April 24, 2012 - 02:55 am:

A generator that will motor is not a guarantee it will generate. USUALLY they will generate but that's not a conclusive test.
It probably would be a good idea to polarize it too after you install it again.......just to be sure....... ;)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Leming on Wednesday, April 25, 2012 - 10:43 am:

guys, tell me a little more or give me a quick lesson on this polarizing business. I always have heard this, but never did it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 25, 2012 - 12:35 pm:

John
To properly work the Model T generator pole shoes must have the correct magnetic orientation with respect to the armature. The relationship of these two magnetic fields allow the generator to create current.
During a generator rebuild if you remove and replace the pole shoes you may not re-install them with the original orientation OR if you change the polarity of the battery you must re-establish the correct magnetic polarity of the pole shoes.
By connecting the battery to the generator it will create a current in the field windings thereby recharging the pole shoes with the new correct magnetic orientation.
Generator pole shoes do not completely loose their magnetic orientation, but there are generator faults that can result in the generator not properly using what exists.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Wednesday, April 25, 2012 - 12:59 pm:

Be aware it the generator is polarized opposite the battery configuration; that is to say a generator polarized positive ground in a negative ground car the output of the generator will be in series with the battery. The voltage across the reverse current relay will double. The voltage becomes equalized on both sides of the cutout and it will start cycling as the voltage drops. Not a good thing particularly if the points in the cutout weld. This brings us full circle to motoring generators. If the vehicle's motor isn't running and the points are stuck the generator wants to motor but cannot. Bad news.

The residual magnetism in the pole shoes is important as it allows the generator to self excite.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Leming on Wednesday, April 25, 2012 - 08:27 pm:

thanks Ron, I wondered, maybe thats what is wrong with mine. I think it has quit working. Dont see an ampmeter charge on mine. To test, cant you remove the battery wire at the cutout and check with a voltmeter between the Generator post and ground for 6 volts?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 25, 2012 - 08:42 pm:

John
Please do not do that!
Give me a call 11am to 4pm EST when I am in the shop and we can discuss.
Ron the Coilman
859-881-1677


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Leming on Wednesday, April 25, 2012 - 08:53 pm:

I'll do that! Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Phil Mino, near Porterville on Thursday, April 26, 2012 - 02:36 am:

Here's a different sort of generator test:

generator test


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Leming on Thursday, April 26, 2012 - 10:36 am:

way cool!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Thursday, April 26, 2012 - 10:43 am:

John your test is exactly what self exciting is all about!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Leming on Thursday, April 26, 2012 - 11:33 am:

Well, explain what is wrong with it? I have a tester that is basically just a voltmeter with a load for testing generators


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