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Old 05-20-2020, 08:05 AM   #1
rer_239
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Default Faulty ammeter

How do I measure generator output ?
Thanks
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Old 05-20-2020, 08:26 AM   #2
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Default Re: Faulty ammeter

For the simplicity of the original ammeters that Ford used, they were actually very sensitive little buggers and could be used to adjust the generator output whenever needed. The modern reproductions are not as sensitive and in some cases just junk. A person would need to replace a junk one or use a sensitive meter made by a reputable company. Electronic ones can be used but they have a tendency to wander in their readings a lot. At least a real mechanical meter will allow a quick visual reference to the output.

The OEM generators had constant output with voltage controlled by the battery and amperage output controlled by the 3rd brush position.
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Old 05-20-2020, 08:44 AM   #3
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Default Re: Faulty ammeter

Ok, but how do I measure output? My ammeter shows discharge when lites are on, but doesn't measure charge when lites are off.
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Old 05-20-2020, 09:46 AM   #4
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Default Re: Faulty ammeter

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Originally Posted by rer_239 View Post
Ok, but how do I measure output? My ammeter shows discharge when lites are on, but doesn't measure charge when lites are off.
It sounds like your ammeter is working correctly if it shows discharge with the lights on.

If you are not seeing any charge with the lights off, and the engine RPM up high enough for the generator to actually be charging the battery, the problem is with your generator or cutout, not the ammeter.

An ammeter is a very simple device. It either works or it doesn't. Now accuracy, that's another thing!
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Old 05-20-2020, 09:50 AM   #5
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Default Re: Faulty ammeter

With the engine RPM at about 20 MPH, no load, what does the meter show? You may just need to adjust the 3rd brush.
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Old 05-20-2020, 11:03 AM   #6
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Default Re: Faulty ammeter

Ok I'll try that
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Old 05-20-2020, 11:44 AM   #7
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Default Re: Faulty ammeter

It is also possible the 3rd brush is not seating properly and making contact on the armature - had that happen.



Also possible the generator became un-polarized?
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Old 05-20-2020, 12:30 PM   #8
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Default Re: Faulty ammeter

Did it work before and then stop or did it never work?

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Old 05-20-2020, 12:43 PM   #9
30 Closed Cab PU
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Default Re: Faulty ammeter

It worked before, but after I adjusted the 3rd brush did not work. Pushed the brush down and then worked. Went into the generator and cleaned/lubed the springs/pivots.


Generator needed a good general internal servicing - lead insulation repair, freshening of wiring contacts, light cleaning of the armature contacts, etc. I had bought it off E bay, issue cropped up after about 3 months use.
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Old 05-20-2020, 04:43 PM   #10
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Default Re: Faulty ammeter

The original cut out switch is turned on by the residual magnetism of the generators field pole shoes. If there is a problem with the cut out or the generator has not been polarized then either could be a problem. Now if it has one of the diodes in a can that looks like a cut out then it could be suspect if the diode went south. There is also a cut out looking device that has a regulator built in which controls the current output. Fun Projects is the company that made those. These units will charge until the battery is back up to snuff then they will reduce amperage automatically so the generator can rest. These won't show much of a charge if the battery is up to full capacity.
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Old 05-20-2020, 06:36 PM   #11
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Default Re: Faulty ammeter

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Originally Posted by 30 Closed Cab PU View Post
It worked before, but after I adjusted the 3rd brush did not work. Pushed the brush down and then worked. Went into the generator and cleaned/lubed the springs/pivots.


Generator needed a good general internal servicing - lead insulation repair, freshening of wiring contacts, light cleaning of the armature contacts, etc. I had bought it off E bay, issue cropped up after about 3 months use.
I'm confused. Are you talking about your own generator or rer_239's generator?
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Old 05-21-2020, 02:13 AM   #12
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Default Re: Faulty ammeter

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I'm confused. Are you talking about your own generator or rer_239's generator?
My generator, thought Charlies post was for me.
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Old 05-21-2020, 08:00 AM   #13
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Default Re: Faulty ammeter

For RER I'd recommend he try to see if the generator motored first. If it motors then chances are it is fine and the problem is probably with the cutout. Just polarizing it would be an easy quick thing to also try.
I agree that the ammeter is probably fine, it seems to work as it should.
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Old 05-21-2020, 10:01 AM   #14
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Default Re: Faulty ammeter

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For RER I'd recommend he try to see if the generator motored first. If it motors then chances are it is fine and the problem is probably with the cutout. Just polarizing it would be an easy quick thing to also try.
I agree that the ammeter is probably fine, it seems to work as it should.
Nice summary
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