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Freewheeling 
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 Topic: 6 volt generator output
Posted: 25 Aug 2023 at 8:27am |
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I rebuilt the 6 volt 3-brush Delco generator on my IB. It has a cutout that closes when the tractors running and open when off. The tractor has the original 3-way switch but the original resistor has been replaced with a 3.3 ohm 10 watt resistor. At half throttle the ammeter pegs out (30+). What could cause this and how do I correct it?
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steve(ill)
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Posted: 25 Aug 2023 at 8:40am |
to start off.... the "A" or Generator terminal goes to the cutout... The "F" terminal is the ground and goes to the light switch ( resistor).. when the resistor is in the circuit you should have low charge or about 2 amps.. When you ground the "F" terminal ( bypass the resistor), you get about 8 amps..
I didnt know that generator was even capable of putting out 30 amps.. You can move the 3rd brush to get it to cut back..
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steve(ill)
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Posted: 25 Aug 2023 at 8:42am |
how to adjust the brush.........
a low or dead battery will effect the charge rate..
https://www.youtube.com/watch?v=PL94VX3GIq8
Edited by steve(ill) - 25 Aug 2023 at 8:45am
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Freewheeling
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Posted: 25 Aug 2023 at 10:31am |
Thanks. I'd heard the 3rd brush was adjustable but couldn't find a "how to". 
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steve(ill)
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Posted: 25 Aug 2023 at 12:47pm |
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im still a little concerned that you can measure 30 amps output on that type generator... but is guess it IS possible ..... amp meter might be off a little also ?
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Freewheeling
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Posted: 25 Aug 2023 at 11:10pm |
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Yup, I was too. The gauge was reading OK before the genny quit working. I tried it twice and both times the gauge pegged out. Hopefully I'll get to the shop tomorrow and adjust the 3rd brush.
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Freewheeling
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Posted: 27 Aug 2023 at 11:47pm |
Help. I'm losing ground on this generator project. I had to remove the unit and pry up the clip holding the ground to get the 3rd brush to move. Put it back on and no matter where the brush is positioned the ammeter pegs out. By the way, the gage max is 20 not 30 as I'd stated before. Had my glasses on this time.  Thought maybe the gage was faulty so opened the switch box to try another gage. Well, the old wire harness rubbed the slot in the switch box and shorted out. Taped it up and closed it back up without changing the gage. Now the ammeter shows max discharge. Zapped the battery terminal on the cutout to the armature post but it still shows discharge. Finally, the cutout now won't close. I'm at wits end. Dang, I hate electrical.
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jaybmiller
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Posted: 28 Aug 2023 at 6:56am |
Steve@B&B will know for sure... I think the field coil is grounded,internally or somehow damaged so that the genny is maxing out on the amps.
a test:...
you disconnect the 'F' wire ( goes to light switch/resistor) do you get ANY amps ??
I'm pretty sure the 'F" control the amps, so if NOT connected , ZERO amps... when grounded... max amps
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steve(ill)
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Posted: 28 Aug 2023 at 7:11am |
Jay is right.. With the "F" wire off.. you get ZERO charge... With the "F" terminal grounded, you get 8 - 20 amps depending on where the 3rd brush is located.. with the 3 ohm resistor in the "F" wire to ground, you get 2-3 amps output.
Only way to get 20 amps out is to ground a wire INSIDE of the generator.
If you get max discharge, i would think the generator is not polarized .... tractor should not be pulling 20 amps while running ( no lights or radio)...... probably INTERNAL SHORT in generator.
You can remove the "F" wire, start the tractor and measure the VOLTAGE output with a volt meter between the two terminals.
Edited by steve(ill) - 28 Aug 2023 at 7:14am
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Freewheeling
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Posted: 28 Aug 2023 at 8:13am |
Hmmm. When I disassembled the generator I noticed that the wire to the field coil from the 3rd brush had been rubbing on the commutator. I coated the wire and made sure it didn't touch when reassembled. I assumed that if it had done any damage, then the generator wouldn't work at all. It sounds as though that trashed my field coil. Yes?
This is my first attempt at rebuilding a generator. The old boy that used to do my mag and genny work passed away and there is no one in the area. Mechanical I can do in my sleep but electrical is too abstract for my brain. Thanks for the lesson!!
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Steve in NJ
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Posted: 28 Aug 2023 at 8:16am |
I'm coming into this a little late, but it sounds to me like you have a grounded arm or field coil inside the Gennie. 30+ amps out of a unit like that is a bit much, and I never heard of that type of amperage being produced from that particular unit. I would go with the 15-20 amp output, but 30+ is a task. Anyway, it's probably a shorted field coil would be my assumption without tearing it down and accessing the unit. No matter how you look at it, you want to get that situation straightened out before you burn up the wiring, Ammeter, and anything else on board the Tractor. The Ammeter is probably already toast. I would change that out no matter what... HTH
Steve@B&B
Edited by Steve in NJ - 28 Aug 2023 at 8:18am
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Les Kerf
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Posted: 29 Aug 2023 at 3:02pm |
 Freewheeling wrote:
... the old wire harness rubbed the slot in the switch box and shorted out. Taped it up and closed it back up without changing the gage. Now the ammeter shows max discharge. Zapped the battery terminal on the cutout to the armature post but it still shows discharge. Finally, the cutout now won't close... |
This is a real puzzler  If I were troubleshooting this unit I would eliminate all of the old wiring out of the equation by disconnecting everything and using jumper wires. Your old wiring obviously is in need of total replacement, but I would verify the rest of the components first. At this point, I would take the generator apart and do continuity tests on the the fields and armature before going live again. If the generator passed the continuity checks, I would connect it directly to the battery and use my inductive amp meter, also have a volt meter connected at the same time. I would test the ammeter by energizing a headlight through it. I am very curious as to where the ~20 amp discharge is going.
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Freewheeling
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Posted: 31 Aug 2023 at 11:02am |
The output was really 20+not 30. Error due to reading at night with no glasses. Duh. Anyway, I set my multimeter @ 20K and the reading with probes on the 3rd brush wire and the F terminal is zero. I thought that meant there was no short and that was good but apparently the should be something like 3.5 ohms resistance. Again, I can't wrap my head around electrical theory but I just want to now if this means I have to replace the field coils. Thanks y'all.
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steve(ill)
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Posted: 31 Aug 2023 at 2:09pm |
Edited by steve(ill) - 31 Aug 2023 at 4:19pm
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Les Kerf
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Posted: 31 Aug 2023 at 2:55pm |
Freewheeling wrote:
...Anyway, I set my multimeter @ 20K and the reading with probes on the 3rd brush wire and the F terminal is zero... |
You will need a meter that can read low Ohms, a X1 scale would be about right
Freewheeling wrote:
I thought that meant there was no short and that was good but apparently the should be something like 3.5 ohms resistance.
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R=V/I The manual specifies ~4 Amps of Field current. 6 Volts divided by 4 Amps = 1.5 Ohms of Resistance. This requires careful use of the ohmmeter to get a good reading, but don't get too hung up on it. Your reading certainly should be in the single digits though.
Freewheeling wrote:
Again, I can't wrap my head around electrical theory but I just want to now if this means I have to replace the field coils.Thanks y'all. |
The field coils may still be ok. I would first carefully inspect (visually) inside the generator to see if there is any place that this wire could be shorted to ground between the Field terminal and the first coil (this alone would cause a maximum generator output). Measure the resistance between the Field terminal and ground. This should NOT be zero. Next, measure the resistance between the Field terminal (no wires connected to it) and the third brush; this is where you should get a low reading but NOT zero. Measure the Voltage of the battery. Make certain that the battery has not reversed polarity (highly unlikely but it HAS been known to happen). Connect the generator using jumper wires WITHOUT going through the stock ammeter as I explained above. Have your voltmeter on the battery and see what it says.
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Freewheeling
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Posted: 31 Aug 2023 at 3:47pm |
Thanks. I read this before going any further. But did I misunderstand this - https://www.youtube.com/watch?v=uMNIbH2bv7w
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steve(ill)
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Posted: 31 Aug 2023 at 4:24pm |
Frank, i erased my post above.. Les is right and your you tube move is correct... I would guess your problem with readings is using the 20K scale.. you need one that is 0-10 ohms if possible..even 0- 100 might work... Number vary between manufactures, but the movie says 3 ohms and Les said over 1.5 ... thats a range... if you read OPEN ( very high resistance).......... or ZERO , dead short, then you have a problem... try a different scale and you get an exact reading..
As LES said, it is normally an external wire that is rubbing the case or brush holder, etc, that causes the problems.
Edited by steve(ill) - 31 Aug 2023 at 4:28pm
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steve(ill)
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Posted: 31 Aug 2023 at 4:37pm |
This is what i was trying to say.. Your third brush is connect thru the coils to the "F" terminal ... If you pull the wire off the "F" terminal and then measure continuity from the 3rd brush to ground, you should NOT see a short.. If the 3rd brush is grounded, then it is similar to the "F" terminal being grounded at the light switch and you will go to FULL CHARGE.. and i think this is what you are seeing ??
FRANK ----I had to remove the unit and pry up the clip holding the ground to get the 3rd brush to move. Put it back on and no matter where the brush is positioned the ammeter pegs out. By the way, the gage max is 20 not 30 as I'd stated before.
This leads me to believe your 3rd brush is grounded / bare wire / not insulated/ etc.
-------------- from my link above...
The 3rd brush connects to the field coil and from there a terminal on the case. This terminal is the one connecting to the light switch or a resistance switch inside the regulator. Your manual may call this terminal F. The F Terminal tells the generator to produce more or less output. Do a continuity check to make sure the 3rd brush is not grounded when the F terminal is disconnected (this does not apply to internally grounded generators without F terminals). If it shows ground when disconnected, your field coil circuit is bad. The next brush should lead directly to a terminal on the case. Your manual may call this Terminal A. The output of the generator comes from this terminal. Do a continuity check for ground. If it is grounded, find out where hopefully the wiring is shorted and if not shorted, you may have a bad armature. 
Edited by steve(ill) - 31 Aug 2023 at 4:50pm
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Les Kerf
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Posted: 31 Aug 2023 at 6:28pm |
Freewheeling wrote:
... Well, the old wire harness rubbed the slot in the switch box and shorted out. Taped it up and closed it back up without changing the gage. Now the ammeter shows max discharge... |
This is what has me concerned. Something happened that is directly related to this. This is why I suggested eliminating the switch box, ammeter, and everything inside it to find out what the generator will actually do. Going from the gauge reading max charge to max discharge is a huge red flag.
Edited by Les Kerf - 31 Aug 2023 at 6:34pm
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Freewheeling
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Posted: 01 Sep 2023 at 2:31am |
FYI I had the generator disassembled. Here's what I found. Setting the multimeter to the lowest (200) setting I got 2.2-2.3 between the 3rd brush wire and the F terminal. After assembly the result was the same. There is no evidence of the wire shorting to ground between the F terminal and the field coil. When disassembled there was no reading of any kind between the F terminal and ground. After assembly I got 3.3.
It's 2:30 AM, I've got to leave for a 6 hour drive in a couple hours, and my brain is toast. Thanks again for all your advice gentlemen. We'll figure this out next week. Have a great weekend.
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