Kubota L2250 Alternator/Regulator no charge

[grandschmu]

Hi everybody,
My L2250 has an 3 wire alternator (B-EFN terminals), it does'nt charge the battery, and I try to understand how it works, how to test the alternator and how to test the regulator. I read some threads but it is often not the same alternator. I read something about bypass but on some thred it say to plug the F terminal to the ground and some others say to put it on the battery... I don't want to blow something, so I prefer to post my question directly myself. Does someone can tell me a step by step procedure to find the problem?
Thanks a lot!

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[Roadworthy]

I can't give you a step by step method of testing but before going too far you should probably clean the battery terminal and the cable connections. Install and tighten them securely. If they'll rotate they're not secure. Follow the ground lead to the frame and clean and tighten there as well. Are you absolutely sure your battery is good? A load test will answer that question. Dirty connectors can prevent a battery from charging. They can also prevent a charged battery from starting the tractor.

 

[grandschmu]

Once the battery is charged externally by a battery charger (Noco Genius), I have no problem to start the tractor or to turn on the light, so the batt is good and I think the connectors are good. When I mesure the voltage on the alternator terminals when tractor is running idle, I mesure:
12,6V on the B (red)
0,1 on the E.
4,1 on the F
4,0 on the N.

That's why I'm assuming the regulator or the alternator has a problem.

If I run the motor at 2000rpm, I have 7V on the N tetminal and still 4V on the F terminal abd the charge lamp is still on.

 

[Roadworthy]

Take the alternator to a starter / alternator repair shop. They can check it out. Depending on the way it's made it could need new brushes. It could also be a failed diode. Of course I won't rule out a failed voltage regulator either but your alternator output sounds low. Some automobile repair shops can also check out alternators.

 

[Williy]

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[number two]

Sure sounds like you need a new alternator-running voltage at B should be about 14V.
Reman unit or repair at starter shop next step.
Good Luck!
Post back please!

 

[Williy]

You could get a one wire alternator
probably cheaper that a new one from
a tractor dealer from the auto parts store.

willy

 

[rScotty]

To the OP, the problem with giving alternator/voltage regulator advice is that there were many different variations. For example, the most common problem is that one of the diodes or brushes has gone bad. Yours shows that symptom.But some alternators have the diodes inside and others on an exterior plate mounted remotely. You will need a Volt-ohmmeter and some knowledge of electricity to go any farther.

And voltage regulators (VRs) can also work in different ways to regulate the voltage on different alternators. VRs are much harder to test than alternators, but just as likely to fail.

That is why you keep getting advice to take it to an alternator rebuilding shop. I prefer a small family business type autoelectric shop.

They will rebuild the alternator, you install it and see it it charges the battery. If not, the next step if for you to replace the VR with an identical type VR.
luck,
rScotty

 

[rScotty]

You could get a one wire alternator
probably cheaper that a new one from
a tractor dealer from the auto parts store.

willy

That's always an option. There are now one-wire alternators available that have the voltage regulation built in.
If the rotation is correct and they fit the space there is no reason why any of these universal alternators won't work with any standard 12 volt car/truck/or tractor.

The industry should have brought out universal combination alternators with voltage regulation a generation ago.

 

[Williy]

They also have alternators with the regulator/diodes
separate so its easy to change and you can also make
your own regulator, just change the diodes

willy