12 volt Delco Generator testing Voltages?

What should I see coming out of the Generator at the armature post grounded to the body? I'm seeing 11.5 and Its a 12 Volt Generator. Obviously it should be more. Is there anything that I should be checking on the Generator internally that may be causing its lacking of Charging? I swear when i first checked it I was getting 25 volts or so. I don't know what happened. I was following the directions in the below link and somewhere along the line I lost the high voltage at the armature post.

Originally I wasn't seeing any positive charge at the Ammeter, just a discharge when the lights were on. I'm pretty sure I don't have a real great ground between the case and the tractor at this point. But I have jumped it for now to get a good ground. Then everything seemed to go wrong. And yes I did polarize the generator. and as I said the most i could get out of it at the armature terminal was 11.5 volts.

http://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=jd&th=458743[/url]

You're right, the open circuit unloaded voltage at the gennys ARM post to case has to be obviously much higher then the 12.6 battery voltage. Whats most important is the voltage it can raise a battery to when that load is attached, NOT the open circuit unloaded voltage.

Of course, the Genny needs a good solid case to tractor frame ground so it can charge the also tractor frame grounded battery.

Next the VR cant work unless it also has a good ground so check and jumper its frame also.

What happens if you jump the gennys FLD post to ground?? If it charges then but NOT otherwise the Genny is okay so the VR is bad or not grounded or the wire from FLD on genny to F on VR is bad.

If it still dont charge when running with FLD grounded and the Genny has a good ground, by pass jump the VR's Cutout Relay by temporarily connecting BAT over to GEN/ARM on the VR. If it charges then but NOT other wise the VR's Cutout Relay is bad or VR not well grounded.

If no charge with VR essentially out of the equation by both jumps above (And wiring and all else is okay), the genny is likely bad.

Possible problems brushes worn too low or commutator covered with grease or carbon or brushes not being held down tight or Fields are open or shorted to case etc etc. The grounded brush inside has to have the flexible braided wire attached to the brush and a good ground.

My Motor test (in my procedure) can indicate if the gennys is good or not.

Is there hot battery voltage on the VR's BAT terminal??? There should be all the time if wiring is right and ammeter good.

John T

Yea, Like I said I Jumped a wire to another place to get a good ground. I might jump with a cable all the way back to the battery to make sure its a REAL good ground.

My Wiring is brand new so there should be no issue there.

No Charge is seen if the field post is grounded.

No charge is seen if you jump from the Armature post to Bat terminal.

I show negative 12 volts to the Bat terminal at the regulator, which I believe is correct for positive ground.

I'm going to open it up I guess to see what I see in side. It had been rebuilt at a shop about 3 years ago with a new regulator and then sat until last week waiting to be installed.

Then if the VR and Genny both have good grounds and the Fld is grounded and cutout relay by passed (BAT over the GEN/ARM) but still no charge,,,,,,,,sounds like a Genny problem. Make sure the brush hold down springys are pushing the brushes down tight against the commutator and its clean n shiny. If you look inside make sure the center tie splice of the two Filed windings is good and NOT shorted to case and brushes and their little flex braided wires are okay.

John T

The output voltage depends on how many amps it has
to supply. Is it hooked to a battery? If you have
a 20 amp load on a 10 amp generator, the voltage
will never come up to spec. Is there any load on
it when tested?

Just running load. The battery was down though. I had run out of gas and just put more in it. I went for another drive and stalled it in a high gear with not enough RPM. At that point it was slow cranking and wouldn't start.

If the battery was in a low state of charge, a good working VR would try to extract the max available out of the genny (i.e. put her into high charge state), but even with its Field dead grounded (max charge), the genny can only produce a finite amount of energy and can only raise battery voltage so much. The VR's cutout relay (if working correct) doesn't even latch closed until the genny reaches a set voltage. If the relay never closes, the genny isn't ever connected to the battery.

You might want to try using a charger on the battery and check it with a hydrometer and maybe a load test to insure its condition and then see what happens. Even a good genny cant perform a miracle on a battery that's completely shot.

As I posted below if the grounds are good and the field is grounded and the cutout relay by passed but still no charge (if battery okay just low) the genny itself is most likely the problem the typical causes of which I also posted.

John T

So I took it apart today and looked it over and everything appears to be fine and clean. I tried the motor test. It spins up not super fast but my battery may be low. Plus I'm using a powerprobe. I attempted to ground the field and I get nothing. If I ground the end at the brush it stops the motor from spinning. I checked the little wire that ties the fields together and it appears to be physically intact. I can't get continuity on it at either end of it. I do get it between the post and the brush end. I'm not sure if I should see it at the small wire or not though.