12 volt Conversion WITH Magneto Farmall A HELP

[DMazur]

Merry Christmas, everyone! Was hoping to get some thoughts on what to do while I have a few days off.

Trying to get the wiring system charging for the first time in decades. Following "John T s Trouble Shoot procedures" on yesterdays tractors. Last Thanksgiving I dragged this tractor out of a wood line.

12 v Gen , Voltage Regulator system with a Magneto (separate). Mag has independent on/off switch works great!

Gen "motors" just fine but instead of speeding up when removing Field wire the motoring stops leading me to believe F is bad on generator. Just placed a New VR 12 v on this tractor.

My ammeter is not reading anything when checking with a volt meter, not positive or negative when running tractor just at 0. do I have it wired incorrectly?

From Generator to VR: F to F. A (armature) to Arm or Gen on VR. Ground on Gen to Ground on VR.

From VR : Bat terminal to - side of ammeter and + side of ammeter runs to the starter.

Bat Terminal and Gr on VR read 12.8 - 13 or more when rpm s high on running tractor.

+ and - ammeter terminals read 6 volts or under and not changing anything on the gauge.

Battery consistently reading at 12.1-12.3 v and never more than 12.30 v.

New VR that is polarized touching Bat and Arm terminals with a spark. all new wiring everywhere. I m a novice so wiring isn t the best you would see but it s all new. No light setup yet.

Ammeter was tested by me with a AA Battery and moved the needle just fine. It s original to a 6volt system mid year Farmall A.

All wire is 12 Ga. I performed a mechanical restoration and wanted this to be able to charge plus add lights. I can t find ANYTHING with a 12v and Mag. Please, help. Thank you all.

 

[Janicholson]

The wiring sounds OK as described. The generator (as described as stopping when the Field is disconnected) is not correct and indicated a fault in the generator. The
residual field pole magnetism coupled with current flowing through the armature from Arm terminal to grounded brush, should produce good fairly high speed motoring. If
the ground brush is not making connection, the field (being grounded through the regulator, or directly when testing) can provide enough ground to allow the armature spin
a little. I suggest the generator (probably brushes) be diagnosed and fixed. The third brush should be adjusted as close to the Arm brush as possible if a 3 brush
generator. Jim

 

[Jim Becker]

(quoted from post at 10:55:51 12/26/23)
From VR : Bat terminal to - side of ammeter . . .

Bat Terminal . . . on VR read 12.8 - 13 or more when rpm s high on running tractor.

+ and - ammeter terminals read 6 volts or under . . .

If I am following everything you said, you are measuring about 6 volts on one end of a wire and 12+ on the opposite end of the same wire. There (almost) has to be something wrong with either that wire or the connections on the ends of it.

A similar observation can be made on the connection from ammeter + to the starter and on to the battery. Are you sure about the voltage readings at the ammeter?

By the way, I also agree with what Jim said about your generator. You may be chasing more than one gremlin.

 

[DMazur]

I will have the Gen taken first thing tomorrow. Only reason I didn t is because when I placed the new VR on and polarized it.. using a volt meter - to VR Ground and + to VR Bat it reads 12.8 or more and that is something I did not see before.

I am not sure what exactly I should "measure" but when I use a volt meter and touch each terminal on the ammeter while the tractor is running it measures voltage of 6 or 3 or 2 volts. The needle on the Ammeter never moves from 0 with high or low RPM.

I have an Ammeter with a plastic bracket so it goes bracket, nut, wire, nut on Ammeters bolt.

But yes, on the Bat VR end it s measuring well over 12.3 but not at the end attached to the Ammeter which is always under 6 v.

 

[BarnyardEngineering]

How are you "measuring the ammeter?"

If you are just touching one probe to each post on the ammeter, you will get 0 Volts, or a very tiny voltage. Touch one probe to an ammeter terminal, and the other to the tractor frame or the battery ground cable connection. You should get nearly the same voltage on each terminal with a digital ammeter.

 

[DMazur]

(quoted from post at 10:42:47 12/26/23) How are you "measuring the ammeter?"

If you are just touching one probe to each post on the ammeter, you will get 0 Volts, or a very tiny voltage. Touch one probe to an ammeter terminal, and the other to the tractor frame or the battery ground cable connection. You should get nearly the same voltage on each terminal with a digital ammeter.

Ah thank you. Now these numbers jump around as I am getting a reading. Overall, they are above 12.3 so mostly 12.7-13.1 whenever I test using a Volt Meter for the Bat Terminal on VR and the Ammeter + wire along with the - wire on Ammeter. All generally reading the same Voltage. This is with the Rpm s highest. Battery stays exactly the same at 12.2-12.3 v during this.

 

[Janicholson]

With a charged battery, the mid to upper RPM charging voltage should be 14.2 to 14.6 volts. less is not going to top off the battery. a bad wire fro VR Bat to amp gauge
will also cause problems, Also a bad amp gauge will cause issues. I still believe the generator is not correct. Jim

 

[Jim Becker]

(quoted from post at 14:44:46 12/26/23) . . . Now these numbers jump around as I am getting a reading. . . .

hat brings up another trap. What sort of voltmeter are you taking these readings with? Digital or analog? Most of the cheap digital meters go nuts if they are anywhere near a running tractor engine. If they can even be read, the numbers are often bad. Expensive digital meters designed for automotive use have filters to handle the interference from the ignition and charging systems. Most (even cheap) analog meters work pretty well as the mass of the needle makes them more stable.

 

[DMazur]

(quoted from post at 19:16:18 12/26/23)

(quoted from post at 14:44:46 12/26/23) . . . Now these numbers jump around as I am getting a reading. . . .

hat brings up another trap. What sort of voltmeter are you taking these readings with? Digital or analog? Most of the cheap digital meters go nuts if they are anywhere near a running tractor engine. If they can even be read, the numbers are often bad. Expensive digital meters designed for automotive use have filters to handle the interference from the ignition and charging systems. Most (even cheap) analog meters work pretty well as the mass of the needle makes them more stable.

DT830B-GT digital multimeter, cheap one from China I must admit. I have noticed the jumpy readings but none have been at an expected level for charging so I still deem things not working correctly. When I have the Genny looked at, I will report back. I don t think I will change anything else for now unless i receive other advice for moving ahead.

 

[Janicholson]

Good point, It takes a professional level investment to get a digital that reads correctly in the very noisy environment of an old
tractor electrical system. Jim

 

[Janicholson]

All digital meters read instantaneous sample voltages. the display indicates whatever it found in that sample. It may sample 10 times
per second, or much more, but it is reading whatever it finds. A meter with a needle, or a digital that has algorithms that can
mathematically compute the voltage from the flurry of samples. There is no likelihood of success finding one that is as high as needed
for charging. A cheap 20 dollar meter with a needle works well. Jim
Home Depot has one.

 

[DMazur]

 

[DMazur]

So, I have taken the old generator to a local shop. It was way too expensive to fix for my budget. I picked up this 12v Delco Remy Remanufactured (almost identical generator) via ebay (a gamble, yes). It has F and A clearly labeled so I have attached my wires from the VR.

Question: Should I have a ground wire from the VR to the Generator? If so, where would I attach that to?

I will tighten the belt, polarize the Generator and the VR and check the gauge for charge tonight. Any other thoughts? Thank you for all the help thus far.

 

[DMazur]

BAT
Arm
F

Are the VR terminals in that order. The Top bolted to the frame of tractor is the Ground Wire that I had previously run to the Generator I am no longer using. Pictures are not good when I attached, sorry about that.

 

[used red MN]

BAT
Arm
F

Are the VR terminals in that order. The Top bolted to the frame of tractor is the Ground Wire that I had previously run to the Generator I am no longer using. Pictures are not good when I attached, sorry about that.

Sorry, this is not an insult, but is your eye sight poor? I can see the identification stampings on the voltage regulator lugs right next to the cover edge. I would hope in person they can be seen much clearer. I can clearly make out the middle one to say “ARM” My best shot at reading the bottom one is “BAT” but no guarantee. The top one has to much glare to read it. I realize the letter stampings are poor. If you have a later model smart phone they have amazing cameras on them, take multiple pictures at varying angles then you can expand the photos to see about anything that require fine detail. When finished you can easily delete them. Otherwise, a low cost magnifying glass is available at many stores to help you to see such things. If the wire is there to ground the VR direct to the generator why not utilize it? It can only help, I would loosen the bolt and get it tucked under the bolt head better.

 

[DMazur]

Sorry about that, rushing while taking care of my newborn so that’ll happen! I grabbed some better photos. I cannot delete or edit … or I would have.

I am young and unfamiliar with VR and Gen setups other than what I research or watch via YouTube. I don’t know where to connect the ground wire on this generator (100409 3A25) and that was what I was asking - guidance on that. Thank you.

 

[used red MN]

The ground is just an additional measure to make sure the connection is good between the voltage regulator and the generator. Instead of going from the generator mount bolt, through the mount bracket to the block, to the clutch housing…etc. there may be a threaded hole right in the generator case. If you find one and use it make sure you have a short bolt to put in there so it only has an 1/8” or a bit more threading into the case. Otherwise one of the mount bolts will be good, the ring connector should go on the bolt so it is right against the generator mounting ear.

 

[wore out]

The ground is just an additional measure to make sure the connection is good between the voltage regulator and the generator. Instead of going from the generator mount bolt, through the mount bracket to the block, to the clutch housing…etc. there may be a threaded hole right in the generator case. If you find one and use it make sure you have a short bolt to put in there so it only has an 1/8” or a bit more threading into the case. Otherwise one of the mount bolts will be good, the ring connector should go on the bolt so it is right against the generator mounting ear.

Some, but not all generators and VR's have ground posts or screws on them.

Yes, there's certainly nothing wrong with a dedicated ground wire between the ground terminal on the generator and the base of the voltage regulator, to keep them at exactly the same ground potential.

 

[DMazur]

I have the 12v Delco Remy Gen and VR back from the shop. The output is 14.5 and above which is great.

I am still having the issue of battery not charging.

Reading the VR Batt terminal along with Ammeter 2 terminals I am reading Generator output which is again 14.5-15 v. My starter reads battery voltage which has been around 12.8-12.9.

I made sure to have my battery charged up and once I remove the charger it will slowly drop staying again around 12.8-12.9.

The Ammeter hasn’t swung in any direction. Stays at 0 but again both terminals are reading Gen. output. 14.5 and higher.

Gen to A

F to F

Bat to Ammeter and other terminal to Starter Lug from Ammeter.

what am I doing wrong? All wiring is new. I have two ammeters doing that same thing if I swap them. Could the both be defective?

The ammeter wire on terminal would be 14.5 and the other end connected to starter lug reads Battery output which would be 12.8 or 13. Could the battery be bad? I had it checked and stated it was good but you know how that can be. What is going on?

This is a 12v system with a magneto. Magneto has a separate on/off switch.

 

[Janicholson]

An ammeter is in fact almost a solid wire internally. that connection should be showing the same voltage on both of the terminals. to assess the ammeter, take off the wire attached to the starter switch. that isolated the ammeter from all connections for testing. turn your Digital volt meter to RX1 and use the probes from the still connected post on the meter to the now no connected post. it should read zero ohms (as though the leads were touching each other) if it does not, the meter is bad. Testing the other meter the same way might also be useful. The meter works by using a short piece of calibrated conductor placed inside to conduct current from one post to the other. this "shunt" is then connected internally in parallel to the meter movement which measures the current passing through the shunt. Jim