04 john deere charging bafflement

[Dave M7040]

OK the alternator is working properly and the regulator is also but it is not charging the battery..
There is a connector (under the dash) that I get 13.2 volts or so out of and 11 .whatever on the other side of it (battery voltage) when I check each side ..(unplugged of course )
There is also a small diode plugged into the wiring harness that I can find on any diagrams but it reads really odd on continuity on my meter ..I am not even sure what it is there for...It reads 0 in one direction and 50 in the other ..
any ideas befor I rip the wiring harness out and start over?

There are one or two diodes in many modern wiring harnesses.

They have nothing to do with the charging system.

They are there to drain off high voltages produced in solenoids and the like where there are coils of wire. Often called flyback diodes.

The magnetic field builds around the coils of wire (i.e. solenoid) and the magnetic field moves the metal part inside the coil. I read you are a Ham guy so some of this stuff is to inform others

When the current is shut off, the collapsing magnetic field acts like a transformer and generates very high voltages in the coils of wire and flows back down the 12 volt system causing damage.

Here are some pictures including one I cut open and replaced the diode. Electronic parts are cheap. tractor parts not so.

I often find on auto ranging multi meters that they are often confused by what scale they should be displaying.

If you put the diode in series with a test light like this one:

You should find the light turning on with one polarity across the diode and nothing the other way.

From Wikipedia:
A flyback diode (sometimes called a kickback diode, snubber diode, commutating diode, freewheeling diode, suppressor diode, suppression diode, clamp diode, is a diode connected across an inductor used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted.

Don't go ripping things apart just yet. Let me re read this thread.

Dave M7040

 

[Dave M7040]

I am waiting for a WSM for your tractor from a friend who may have one.

Possibly the connector is a fusible link and it is blown.

That way you would see battery voltage on one side and charging voltage on the other but nothing is going through the link.

The fusible link is like a slow blow fuse used on newer machines. It utilizes a short piece of lighter gauge wire covered by a special insulation.

The small wire melts but the insulation remains in place so the burn off ends of the wire don't spark against anything.

Here is a picture of one

Dave M7040

 

[Dave M7040]

Can you post some pictures showing the alternator or dynamo, the starter, battery and cables.

Are you working from a WSM or wiring diagram? If so can you make it available to me so way.

There will NOT be a charging relay!

Dave M7040

 

[Dave M7040]

Just so you know ..I am an extra class ham radio operator (not bragging just so you know I know how to use test equipment etc.)
The thing that really confuses me is a connector that has like 8 gauge wire going to it..
If I uncouple the connector ..one side reads 13+ volts (common sense would say that is the output from the regulator)
The other side of the connector is the same as the battery voltage..
If you connect a amp meter from the 13+ volt side (no current) it will not even light a test light..
If you put a amp meter between the two (13+ volt side and the side that is reading battery voltage no current ) I even put my test lamp between the two ..no go
You would think that that would be the wire that monitors the battery voltage (if so why such a large gauge wire)
I am about to tear the whole wiring harness apart and trace every wire..
I know its something stupid that I am blind too..
The person I bought this tractor from replaced the motor and battery ..it could be as simple as a ground wire that was not replaced ...
Any ideas????Thanks

TN


What model of motor was in it originally, a Yanmar 3TNE74?
What model is in it now?
My friend does not have a WSM for that series of JD so any wiring diagram or manual info you can provide will get you far better info.

Dave M7040

 

[Dave M7040]

I now realize I have a WSM for a series of Yanmar engines.

One is close to yours as 3TNV76 whereas tractordata shows your engine as 3TNE74

You likely have a dynamo not an alternator which is why I need some photos plse.

Dave M7040

 

[Joe Cannon]

Dave yep the diodes seem to be there to suppress the solenoids (as they act like ignition coils when the magnetic field in them collapses..
I have not found any fuse-able links yet but I am going to start taking the wiring harness apart and start tracing wires..
I have ordered a service manual...
The other odd thing is ...there is only one fuse in the fuse block out of 4 that is hot when the tractor is running...
Like you ...I think there is a bad wire or connector fuseable link somewhere I have not found yet...
(just a side note) in some cases diodes are also used in safety shut down circuits in some equipment )
Thanks for all your help

 

[Joe Cannon]

Photos any one know what each relay is for? Thanks again...
View attachment IMG_20180217_103142530.jpg
View attachment IMG_20180217_103202693.jpg
View attachment IMG_20180217_103218666.jpg

View attachment IMG_20180217_103300360.jpg
View attachment IMG_20180217_103311120.jpg

 

[Joe Cannon]

FOUND THE PROBLEM!!!!!
There is a relay right next to the voltage regulator ...I swapped it out with one just like it from the other side of the tractor (no idea what that one is for yet but its charging !!!!! no idea how to order a new one as there are no markings on it at all lol

 

[Sparkynutz]

Parts breakdown of the tractor should get you a part number. Glad u found it!

 

[Dave M7040]

FOUND THE PROBLEM!!!!!
There is a relay right next to the voltage regulator ...I swapped it out with one just like it from the other side of the tractor (no idea what that one is for yet but its charging !!!!! no idea how to order a new one as there are no markings on it at all lol

Although you found the cause of your lack of charging, my friend just came up with a WSM.

For the future, here is the charging circuit.

The tractors wiring has about 8 diodes including V6

The safety relay K3 and its diode V6 is to protect the regulator from reverse battery polarity.

The WSM also comments:
Diodes usually fail in the open position but can fail shorted. If any problems in charging circuit check both V6 and V8 diodes.

I expect the relay would be the same as most automotive headlight relays.

I am surprised the relay was the issue as it is just a battery voltage sensing circuit carrying no real power that would burn the contacts.
Here is the list of relays:

K1 - Start Relay (SE1, W1)
K2 - Fuel Relay (SE2, W1)
K3 - Safety Relay 1 (SE3, W1)
K4 - Safety Relay 2 (SE3, W1)
K5 - Flasher (SE4, W1)

Do you need more help?

Dave m7040