8N not charging

[dkkj]

My 8N is not charging. I followed the steps in the manual (jumping various terminals at the regulator, etc.) and determined the generator was the problem. I dis-assembled the generator and found it to be in really nice condition on the inside (most generators I've pulled apart had 50 years of rigging, dirt, & wear on the inside). I checked the field coils for continuity: good. Checked the field coils for continuity to the housing (a short): good, no continuity.

However, when I connect an ohm meter between the field coils and the housing, I get 3.95K ohms. Is that normal? Shouldn't the ohm meter read infinity? Don't think I've ever come across this situation before.

See picture for for further details.

Thanks.

This post was edited by dkkj on 07/16/2022 at 02:24 am.

 

[JMOR]

(quoted from post at 14:41:49 07/15/22) My 8N is not charging. I followed the steps in the manual (jumping various terminals at the regulator, etc.) and determined the generator was the problem. I dis-assembled the generator and found it to be in really nice condition on the inside (most generators I've pulled apart had 50 years of rigging, dirt, & wear on the inside). I checked the field coils for continuity: good. Checked the field coils for continuity to the housing (a short): good, no continuity.

However, we I connect an ohm meter between the field coils and the housing, I get 3.95K ohms. Is that normal? Shouldn't the ohm meter read infinity? Don't think I've ever come across this situation before.

See picture for for further details.

Thanks.

he 2 statements leave me not knowing to believe continuity or no continuity?
Checked the field coils for continuity to the housing (a short): good, no continuity.
However, we I connect an ohm meter between the field coils and the housing, I get 3.95K ohms.
I suppose it is in one's definition of continuity, perhaps. 3.9K is continuity, as is 1 meg Ohm. So yes, there is some continuity from fields to case & there should be none, i.e., infinity. Not a direct short, but likely leakage through bad insulation, dirt, etc.
Don't know for sure, but it might keep it from charging? Measure the current thru field and repeat with either (one at a time) field terminal jumpered to case. Different currents?

 

[Abbby]

Slippery slope spending too much money on an archaic 6 volt system. Switch to 12 volt and get an alternator.

 

[dkkj]

(quoted from post at 15:34:58 07/15/22) The 2 statements leave me not knowing to believe continuity or no continuity?

When the meter is set on "ohms", I get 3.95K ohms. (shown in picture)

When the meter is set on the "diode test, continuity" position, it does not beep. It's the next position on the meter in the picture.

 

[dkkj]

(quoted from post at 20:04:16 07/15/22) Slippery slope spending too much money on an archaic 6 volt system. Switch to 12 volt and get an alternator.

No it's not. 6 volts works just fine on a whopping 120 CID, 6:1 compression engine. Besides the entire tractor is archaic. Based on your assessment, I should just junk it and get a new JD with 12 volts, live PTO, power steering, Diesel engine, etc. Not trying to be an ******* but nothing looks worse than a Delco alternator hanging off the side of an antique tractor.

 

[Tim PloughNman Daley]

How did you determine the GEN wasn't charging? What does your AMMETER show when running at idle? At throttle up under load? You should motor test the GEN first, an
easy no-cost procedure, or take to your local, trusty, starter/alt shop guy who knows old FORDs to be tested. Did you turn the commutator? You don't mention new
brushes. Did you replace? All 8N's used a 3-Wire GEN with a Voltage Regulator. Early 8N models used a 3 Brush, 11 AMP, A Circuit unit and the later 8N GEN was changed
to a 20A, 2-Brush unit. The 3rd Brush was eliminated as it wasn't needed and the adjustment screw was dissolved on the back end plate. There is a FORD SERVICE BULLETIN
that details how to remove the 3rd Brush and make your old GEN into a 2 Brush unit. New brushes are available in solo or a kit form. Polarizing the GEN should always
be done once all the wiring is correct and before powering up. Your post about your GEN would indicate you are using the OEM 6V/POS GRN electrical system but I won't
assume.

Tim Daley(MI)

 

[JMOR]

(quoted from post at 05:35:10 07/16/22)

(quoted from post at 15:34:58 07/15/22) The 2 statements leave me not knowing to believe continuity or no continuity?

When the meter is set on "ohms", I get 3.95K ohms. (shown in picture)

When the meter is set on the "diode test, continuity" position, it does not beep. It's the next position on the meter in the picture.

o the current test that I described

 

[dkkj]

(quoted from post at 07:46:06 07/16/22) How did you determine the GEN wasn't charging? What does your AMMETER show when running at idle? At throttle up under load? You should motor test the GEN first, an
easy no-cost procedure, or take to your local, trusty, starter/alt shop guy who knows old FORDs to be tested. Did you turn the commutator? You don't mention new
brushes. Did you replace? All 8N's used a 3-Wire GEN with a Voltage Regulator. Early 8N models used a 3 Brush, 11 AMP, A Circuit unit and the later 8N GEN was changed
to a 20A, 2-Brush unit. The 3rd Brush was eliminated as it wasn't needed and the adjustment screw was dissolved on the back end plate. There is a FORD SERVICE BULLETIN
that details how to remove the 3rd Brush and make your old GEN into a 2 Brush unit. New brushes are available in solo or a kit form. Polarizing the GEN should always
be done once all the wiring is correct and before powering up. Your post about your GEN would indicate you are using the OEM 6V/POS GRN electrical system but I won't
assume.

Tim Daley(MI)

Answers to your questions (in order I think):
Connect volt meter to battery. Start engine. Increase to half throttle. No increase in voltage = not charging.

Ammeter is just a decoration (a.k.a. it doesn't work).

Past experience with my "local, trusty, starter/alt shop guy" haven' t been good. His repairs don't last: voltage regulator failure and/or bearings howling in less than a year. I've built a well equipped shop over the years and now do my own repairs. I have a lathe, Jacobs commutator turning chuck, growler, bearing/bushing pullers, etc. And hammers...lots of hammers.

I didn't mention new brushes or turning the commutator because I only just disassembled the generator & started testing for shorts/opens/etc. However, the commutator looks great (will require only a lite polish) & the brushes look new.

It's a 6 volt, positive ground, 2 brush generator. Generator was polarized per the manual before any testing was done. Diagnostic procedure was followed per the manual.

 

[dkkj]

o the current test that I described[/quote]

What do you mean by "current test"? Do you mean "ohm test"? I understand connecting one or the other field lead to the housing as depending on where the "weak insulation" is, it will change the reading.

 

[JMOR]

(quoted from post at 14:04:42 07/16/22) o the current test that I described

ote, only one jumper at a time, not both together. The heavy black connection simulates the bolted chassis connection when mounted on tractor & should remain in all 3 test/measurements.

This post was edited by JMOR on 07/17/2022 at 05:33 am.

 

[dkkj]

Thank you for the generator lessons. Past repairs have been limited to obvious bearing problems and/or worn commutator/brushes. Never had to dig deeper than that. Testing will commence on Tuesday.

 

[JMOR]

(quoted from post at 13:15:17 07/17/22) Thank you for the generator lessons. Past repairs have been limited to obvious bearing problems and/or worn commutator/brushes. Never had to dig deeper than that. Testing will commence on Tuesday.

ust FYI, my not expensive $50 meter instruction booklet says Continuity is indicated when resistance is below 300 Ohms. No doubt, all meters are not the same. Also, 3.95K Ohms and 6 volts is only 1.6 milliamperes & I don't see that as a charge killer.

This post was edited by JMOR on 07/17/2022 at 02:50 pm.

 

[dkkj]

Just FYI, my not expensive $50 meter instruction booklet says Continuity is indicated when resistance is below 300 Ohms. No doubt, all meters are not the same. Also, 3.95K Ohms and 6 volts is only 1.6 milliamperes & I don't see that as a charge killer.

Dug out the manual for my meter. It reads "Continuity is indicated when resistance is below 150 Ohms." Learn something new everyday. Thanks.

Update: The fuse (for taking amp readings) in my meter blew about 25 years ago. Amazon will deliver new fuses this Friday, so I can't do a current draw test until then.

I did find some minor aluminum corrosion at the brush ground screw. Not bad corrosion but still some. I cleaned everything and reassembled. I did a motoring test and it worked so I'm hoping the corrosion was the problem. I won't know until I get my governor repaired and reinstalled.

Thanks for the help so far. I'll post updates as I can.

 

[Hobo,NC]

That M on yer meter will get ya : ( me thinks you are chasing a ghost.

I thought I was the king of blowing fuses in my meter...

Nuttin else to add other than y'all keep up the good work...