Generator voltage question on a 1948 8N

My genny is a three lug type. Field and Grd on the can and ARM on the end. No current adjustment screw. Haven't opened it yet so don't know if it is a 2 or three brush.

My amp gauge always reads a slight bit on the discharge side when engine running. I have no lights.

Troubleshooting:
Volt meter on battery reads the same 6.33v after battery manually charged whether engine running or not.

With engine started and around 1200rpm. I put my volt meter across the ARM and grd (either the GRD lug on generator or chassis bolt), I expect to get at the very least 6 Volts but actually measure 0 volts.

If I jumper ARM and BAT at VR I measure battery voltage (6.33 v) at the generator ARM to GRD.

I remove ARM to BAT jumper at the VR and disconnect field wire from VR at the generator and connect another wire to generator field lug and to grd and still measure 0 volts across the ARM.

-My meter is fine. I have a few flukes and Beckmans that I have
used in the field for years.
-All my connections are tight and bright.
-Replaced all old connectors and re-soldered them.
-Wires are not old and cracked.
-Ohm'd out wires from genny to VR and readings show no open readings


My question is, I want to isolate the generator from the electrical circuit and want to make sure that the genny is putting out 6+ volts? I would have thought just running the generator with all wires disconnected and a VM across the ARM and Field lugs on the generator should have given me a reading.

What am I missing.
 
(quoted from post at 09:28:10 08/25/14) My genny is a three lug type. Field and Grd on the can and ARM on the end. No current adjustment screw. Haven't opened it yet so don't know if it is a 2 or three brush.

My amp gauge always reads a slight bit on the discharge side when engine running. I have no lights.

Troubleshooting:
Volt meter on battery reads the same 6.33v after battery manually charged whether engine running or not.

With engine started and around 1200rpm. I put my volt meter across the ARM and grd (either the GRD lug on generator or chassis bolt), I expect to get at the very least 6 Volts but actually measure 0 volts.

If I jumper ARM and BAT at VR I measure battery voltage (6.33 v) at the generator ARM to GRD.

I remove ARM to BAT jumper at the VR and disconnect field wire from VR at the generator and connect another wire to generator field lug and to grd and still measure 0 volts across the ARM.

-My meter is fine. I have a few flukes and Beckmans that I have
used in the field for years.
-All my connections are tight and bright.
-Replaced all old connectors and re-soldered them.
-Wires are not old and cracked.
-Ohm'd out wires from genny to VR and readings show no open readings


My question is, I want to isolate the generator from the electrical circuit and want to make sure that the genny is putting out 6+ volts? I would have thought just running the generator with all wires disconnected and a VM across the ARM and Field lugs on the generator should have given me a reading.

What am I missing.

Skip the VR and run jumper from gen field to gen gnd AND jumper from battery to gen arm. With belt loose, the gen should "motor"........if it doesn't, time to look inside. If it does, then tighten belt & start with same two jumpers in place & monitor battery voltage, looking for about a volt increase over a period of a couple of minutes at speed.
 

JMOR I have the generator sitting on my work bench.
Where I was going with this is, I want spin the generator with my 1/2 drill via a socket on the generator pulley nut and measure voltage generated.

Motoring the genny is a good test but doesn't tell me that the the gen is really producing volt-amps.
 
You already know that you generator is not producing any voltage, now you need to find out why and a motoring test will help in that regard. Since you have it off the tractor I would would just take it to a repair shop and have it checked/repaired. Brushes are easy to change but unless you have a lathe to turn the commutator it would be best to take it to a shop. They can check the armature also. The last one I tried to repair ending up going to the shop. found out the armature was bad.
 

Sorry but old tech habits die hard..... I need to prove it to myself If am I correct in assuming that a voltage check across the ARM and FIELD while the gen is being spun should give me a voltage reading?
 
(quoted from post at 09:51:04 08/25/14)
JMOR I have the generator sitting on my work bench.
Where I was going with this is, I want spin the generator with my 1/2 drill via a socket on the generator pulley nut and measure voltage generated.

Motoring the genny is a good test but doesn't tell me that the the gen is really producing volt-amps.
robably not fast enough, but even slow will show something. Same as I outlined: jumper field to gnd, measure arm to ground. When unloaded, the arm voltage can reach 17-20 volts if near rated speed, when no battery or VR in circuit.
Even this is below rated speed:
 
(quoted from post at 11:29:18 08/25/14) If you ground the F terminal with the motor running
it should charge full amps if not the gen is bad.
enry, that 'assumes' that the cut out contacts/function of the VR is all OK & working as they should.
 
motor test genny.


ground case, ground field.

jumper bat to arm

it should spin. if it won't spin.. it won't charge.
 
Thank You:That is true, you have to have a path for
the amps to flow back to the battery I know on my 8N
it had sat for a while and would not charge ,thanks
to Soundguy I grd the F and it started to charge
right away
 
ator

JMOR ....I had the generator spinning at about 3500rpm thanks to my the wire wheel on my grinder. The genny never put out so much as 1/2 volt

SoundGuy....I couldn't motor the genny since my son has my battery charger, battery pack is dead and tractor is 125 miles away.

Tomorrow is another day.
Thanks for all the help.
 
(quoted from post at 21:14:52 08/25/14) ator

JMOR ....I had the generator spinning at about 3500rpm thanks to my the wire wheel on my grinder. The genny never put out so much as 1/2 volt

SoundGuy....I couldn't motor the genny since my son has my battery charger, battery pack is dead and tractor is 125 miles away.

Tomorrow is another day.
Thanks for all the help.
ime to open it up & take a look-see. I feel certain that you are spinning in correct CW (facing pulley) direction.........if NOT, then zero output is normal.
 
Yep...Clockwise facing the genny.

Against my better judgement before motoring as SoundGuy suggested, I took her apart and cleaned her up. Commutator was very clean. No pits, rust or worn spots. Took some sand paper and gave her a light polish.
Armature was rusty so I gave her a rub down with some sand paper till it cleaned up and noticed a "REBUILT" stamped into one of the armature plates.
Bearing and bushing had very minor play when disassembled but very very little when the genny was assembled and spinning on both bushing and bearing.
Brushes were about 1". Not worn cracked or broken.

I tested for shorts and grounds based on the Ford 8N manual but found none.
Ohm'd for frayed wires, brush springs holders and all checked out OK

Put her all back together and still no volts when I spun her.
Gonna try to motor her tonight.

I hate when I cant figure something out on my own.

I found a place close by me here in Queens NY called Mondial that are based out in Franklin IN that will test it for me.
http://www.gomondial.com/

BTW: Are these Delco Remy generators?
 
If it has not been swapped at some time in last 65 years, then it ia a Ford generator. Can you connect a battery from field to arm and obtain current flow?
 

Gonna hook up a battery and my amp meter tonight to motor it and see if it is drawing current and how much. Which reminds me. I blew my 20 amp mini fuse out my fluke meter while back ago.
 
OK...attempted to motor the generator tonight. I only had access to a 12 volt battery. The armature did not spin other than give a very slight jerk with either the field grounded or not grounded.

With the battery connected, I was able to spin the pulley with no resistance felt.

My amp meter measured 3.65 amps max draw at 12 volts so thinking around 7.5 amps if I was trying to motor with a 6 volt source.

Done as much as I can. Gonna take it to the shop tomorrow. My guess is the armature is grounded and no good.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top