Farmall 826 Electical issue.

[brahamfireman]

Rereading other post, I misinterpreted and it sounds like the old 10DN alternator is being used.

Your voltage regulator is probably bad, but we still need to figure out how this voltmeter is wired in.

[HydroTek]

12 hours ago, acem said:

Turns out I have 2V between my alternator case and engine block/ground. Never had that problem before. 

I'll run a ground wire to the block.

 

More common problem than you are thinking 

Had an '88 that the customer put  new alternator on -- "still not charging"
-- one would think that between the mounting bolt or the belt tightening bracket , the alternator would have made ground

[HydroTek]

13 hours ago, brahamfireman said:

Can't say I've seen many with the R and F markings, most are 1 and 2.

Seen them with both markings R1 - F2 
-- seems like other things that marking changed over the years 

You should be asking if there is the flat plug or is it square to identify the alternator 

Many tractors still have the factory regulator , but are using the 10SI internal 
-- just have the wires jumpered at the old regulator 

[IHC_1470]

19 hours ago, jim dog said:

There are four wires that attach to the back,the two small wires are attached to two wire plug and plug in at the top of the back which are marked R and F. there is also the battery wire and a ground wire.

So what voltage reading do you have on the small plug? Key on and key off.

[jim dog]

4 hours ago, brahamfireman said:

Where is the guage located?

Only factory guages in the dash are big round tach on the left and the big combo fuel/temp guage on the right. 

For the 3rd time now......is the factory regulator still installed in the pedestal between the pedals?????

Yes the voltage regulator is in the pedestal.

[snoshoe]

4 minutes ago, jim dog said:

Yes the voltage regulator is in the pedestal.

Did you find a diagram? I can't post a pic and seem to have lost the ability to create a link now. I can try to describe the circuit if necessary. 

[jim dog]

2 hours ago, IHC_1470 said:

So what voltage reading do you have on the small plug? Key on and key off.

I did not test the two small wires in the small plug. I did check the voltage on the large wire that goes to the solenoid, i was reading 20 volts. I found the regulator was bad.With the new regulator i still had the amp lite on.

[acem]

6 hours ago, brahamfireman said:

It's Not possible to use the external regulator and have an internal regulated alternator work correctly.

Works  great with a single wire 10SI.

Hook up the charging wire and leave the other connector unhooked. The battery stays properly charged.

These are open station tractors with small to no electric loads.

 

[jim dog]

On 8/28/2026 at 8:27 AM, brahamfireman said:

Where is the guage located?

Only factory guages in the dash are big round tach on the left and the big combo fuel/temp guage on the right. 

For the 3rd time now......is the factory regulator still installed in the pedestal between the pedals?????

sorry I meant to say voltage regulator.

[jim dog]

On 8/28/2026 at 9:18 AM, brahamfireman said:

Rereading other post, I misinterpreted and it sounds like the old 10DN alternator is being used.

Your voltage regulator is probably bad, but we still need to figure out how this voltmeter is wired in.

I just replaced the voltage regulator,there is no volt meter only a Amp lite. With the new regulator the amp lite is still on. i just had the alternator tested they said it was fine.

[jim dog]

On 8/28/2026 at 1:23 PM, snoshoe said:

Did you find a diagram? I can't post a pic and seem to have lost the ability to create a link now. I can try to describe the circuit if necessary. 

I did find a diagram for a 806 with a alternator it seems real close to what i have.

[acem]

I thought there was a wiring diagram in the owner's manual...

I reserve the right to be wrong!

[snoshoe]

2 hours ago, jim dog said:

I did find a diagram for a 806 with a alternator it seems real close to what i have.

OK just to help you understand. Power comes from key switch to tell light. The blue wire carries that power from tell light to number 4 terminal on regulator. Power has to come back out F terminal of regulator. That will be the yellow wire and will go to F terminal of alternator. This is field current to start alternator. Once alternator starts half wave rectified half voltage current is available at the R terminal. That is carried by the brown wire back to the 2 terminal on regulator where it closes a relay inside and the light goes out. My suggested procedure; we know we have power to the light because it is on. We know it is grounded for the same reason. Check voltage at regulator terminal 4. No voltage wire is grounded between regulator and light. If you have voltage go to F terminal. No voltage grounded inside regulator. Have voltage go to F terminal of alternator. No voltage wire grounded between regulator and there. These test were done engine off key on. If you had voltage at the F terminal. Start engine you may have to rev it a little. Check voltage at R terminal should be half of what is on bat terminal. If not there is still a problem with alternator even if it is charging. If it is there. Then check voltage at terminal 2 on regulator. By now you should have the problem pinned down.

Before you start. I would have you check the regulator plug closely.  Make sure all 4 regulator terminals are straight and in line. Make sure both ends of the plug are fully seated and the plastic lock is locked. Lastly Make sure all 4 wires are fully seated in the plug.

[snoshoe]

That was a lot of typing but I think It's only 4 probes with a volt meter. 2 minutes should do it.

[HydroTek]

Pull the plug out of the alternator -- the dash light should go out 

[snoshoe]

5 minutes ago, HydroTek said:

Pull the plug out of the alternator -- the dash light should go out 

Yup but he still don't know if it's alternator, brown wire or relay.

[jim dog]

On 8/30/2026 at 12:19 AM, snoshoe said:

OK just to help you understand. Power comes from key switch to tell light. The blue wire carries that power from tell light to number 4 terminal on regulator. Power has to come back out F terminal of regulator. That will be the yellow wire and will go to F terminal of alternator. This is field current to start alternator. Once alternator starts half wave rectified half voltage current is available at the R terminal. That is carried by the brown wire back to the 2 terminal on regulator where it closes a relay inside and the light goes out. My suggested procedure; we know we have power to the light because it is on. We know it is grounded for the same reason. Check voltage at regulator terminal 4. No voltage wire is grounded between regulator and light. If you have voltage go to F terminal. No voltage grounded inside regulator. Have voltage go to F terminal of alternator. No voltage wire grounded between regulator and there. These test were done engine off key on. If you had voltage at the F terminal. Start engine you may have to rev it a little. Check voltage at R terminal should be half of what is on bat terminal. If not there is still a problem with alternator even if it is charging. If it is there. Then check voltage at terminal 2 on regulator. By now you should have the problem pinned down.

Before you start. I would have you check the regulator plug closely.  Make sure all 4 regulator terminals are straight and in line. Make sure both ends of the plug are fully seated and the plastic lock is locked. Lastly Make sure all 4 wires are fully seated in the plug.

Snoshoe I had voltage on all the items you had me test. on the regulator #4-4.45v  #3-12.25v  #-2-.550 #F4.45v running 6.14v. Someone stated if you pull the two wire plug on the alternator the lite will go out. I tried it and it didn't go out. With the alternator running it does develop a magnet on the back where the bearing is. Does that mean its charging?

[snoshoe]

9 minutes ago, jim dog said:

Snoshoe I had voltage on all the items you had me test. on the regulator #4-4.45v  #3-12.25v  #-2-.550 #F4.45v running 6.14v. Someone stated if you pull the two wire plug on the alternator the lite will go out. I tried it and it didn't go out. With the alternator running it does develop a magnet on the back where the bearing is. Does that mean its charging?

Did you pull the plug with it running or not running. If not running then light is grounding somewhere other than the alternator. Did you confirm the wire colors were at the terminals I called out.

The magnetism says the alternator is doing something. I would need battery voltage or R terminal voltage while running to guess what.

[brahamfireman]

8 minutes ago, jim dog said:

Snoshoe I had voltage on all the items you had me test. on the regulator #4-4.45v  #3-12.25v  #-2-.550 #F4.45v running 6.14v. Someone stated if you pull the two wire plug on the alternator the lite will go out. I tried it and it didn't go out. With the alternator running it does develop a magnet on the back where the bearing is. Does that mean its charging?

I'm pretty sure the light is controlled by a contact in the voltage regulator, try unplugging the voltage regulator and see if the light goes out. 

If it's magnetic on the back bearing then yes it's charging,  but it might just be charging from residual magnetism and not regulating. Check output voltage with a multimeter.

[acem]

1 hour ago, jim dog said:

 With the alternator running it does develop a magnet on the back where the bearing is. Does that mean its charging?

Normally yes. If it's magnetized it's charging.

However that actually means the armature is energized, creating the magnetic field. 

I have had a failure in the rectifiers? It was magnetized but not charging.

I have so have used so many Delco alternators in so many applications that I have seen many various issues. However the most common is the voltage regulator and brushes/holder.

They are usually very easy to repair.

[jim dog]

On 8/31/2026 at 10:53 PM, acem said:

Normally yes. If it's magnetized it's charging.

However that actually means the armature is energized, creating the magnetic field. 

I have had a failure in the rectifiers? It was magnetized but not charging.

I have so have used so many Delco alternators in so many applications that I have seen many various issues. However the most common is the voltage regulator and brushes/holder.

They are usually very easy to repair.

Acem , Do you think by having the wrong bulb in the tellite could be my problem .The last owner had LED bulb in it The proper bulb  has the  two pins at different height's. The LED bulb has the pins at the same height.  You do control the bulb from the negative side as well from the positive side. Does anyone have the number for the AMP tellite bulb?

[IHC_1470]

I believe they were a 257 bulb. A LED bulb very well could be the issue as like any diode they only allow current flow going one direction. 

[acem]

Very possible an LED will not work.

The bulb acts as a resistor and provides voltage to initiate charging.

I don't think a LED will let enough voltage through to the regulator but I'm not sure.

My information above is based on my experience with 10SI alternators with internal regulator. The external regulator alternators may be different.

 

[acem]

If we had pics, this thread would help.

 

[snoshoe]

Alternator will work with out the bulb. That is what the resistor by the regulator is for. It allows the alternator to work even if the bulb is burnt out or missing. Follow the steps I laid out in the order I laid them out. Verify colors are at terminals I called out and we will know where problem lies.