Alternator / Battery light always on, B2920

[SnowRidgeME]

My alternator light on the instrument panel is always on. Battery voltage when tractor is running is 14.6 volts, so I know my alternator/dyno (whatever it is) is charging. Tightened the belt to be sure. Any ideas? Issue just started this weekend, 75 hours.

 

[leonz]

Loose battery cable?

You can have a broken cell in the
battery too and the battery will not
fully charge.

 

[kuboman]

My alternator light on the instrument panel is always on. Battery voltage when tractor is running is 14.6 volts, so I know my alternator/dyno (whatever it is) is charging. Tightened the belt to be sure. Any ideas? Issue just started this weekend, 75 hours.

Check your battery connections especially the ground. You may also have a VR that is crapping out.

 

[moship]

If all the traditional fixes don't pan out perhaps keep this in mind. My neighbors B9200 suffered from a charge indicator lamp continually being illuminated. the tractor is 25 years old and from what he remembers it was always on... He even thought this was the standard mode of operation. Everything else was OK. Batteries lasted their normal life and didn't seem to have any real charging issues. Knowing this was not the correct way this should be woking, I dug into the wiring harness. As it turns out one of the connections at the multipin connectors was not making adequate contact with each other. Since the wiring harness was never touched (I unwrapped the old degraded tape) it had to come from the factory this way. Some how the male portion did not engage with the female end on one of the individual wires. It slide along the side of it. Fixed the connection and the light went out. It's been two years and the light never reappeared.

I'm not saying this is your problem, but perhaps this will provide a clue should all else fail.

Having a detailed wiring diagram really helps when trouble shooting electrical problems.

Good luck and remember to let us know the solution.

 

[Craig Clayton]

My L2250 Kubota has a sensor that is in the second cell of the battery to check the level of the electroylite. When I replaced the battery with a Volvo screw top cell, I had to put a small hole through the cap to install the sensor to keep somthing happy on the panel. It is a single wire check water level.
Craig Clayton

 

[abeal]

Do you have another battery you could try?

 

[SnowRidgeME]

Report: Thank you for the info. Well I have cleaned the battery posts, and the ground connection, no improvement; I connected a battery charger, light stays on still. Fuses are fine. I tried connecting to my truck battery with jumper cables, but did not get a good enough connection to start the tractor. If a cell was bad, wouldn't the battery voltage be lower? It is about 12.55 volts not running, 14.6 running. I should put a load on it though, which I'll try tomorrow. I've ordered a shop manual, hoping that an electrical schematic is included. Do you think I could ruin something by using it? Any other ideas?

 

[OrangeRidge]

You have Factory Warranty on this unit . This should be a dealer fix ?

 

[ibnxe]

There is nothing wrong with your battery if you are reading 12.55 volts, not running, and 14.6 volts running. The 14.6 volt reading indicates that the alternator is functioning. You are not going to hurt anything by running the tractor.
With only 75 hours on the clock, I would be checking in with the dealer.

 

[SnowRidgeME]

still waiting for my service manual to see the schematic... called the service department, tractor is out of warranty, he suggested the obvious, battery Ok, charging, belt, which I have all checked, but he also wondered if it could be a bad diode in the dynamo. If a diode was bad, then I would think that it wouldn't be charging at 14.6 volts. Any one agree/disagree?

 

[moship]

Using a conventional volt meter it may not be possible to see what is going on with voltage alone. Keep in mind the alternator output is AC and is rectified by the diodes to simulate DC. In reality it is somewhat dirty and looks like a series of truncated sin waves. The indicator light works on a voltage differential. If none exists the light will not illuminate.

There could be a number of reasons why the charge indicator is illuminated in your case. Yes, a diode could be bad causing the light to illuminate and it could also generate a voltage of 14 volts. For 2/3rds of wave it might be ok (truncated positive sin wave) and then be a sin wave going through zero volts for the other 1/3 (pure sin wave). The typical digital volt meter is overly damped and will never see this, but an oscilloscope or some of the high end volt meters that have graphing capabilities can. There are typically 6 diodes in the common alternator design.

Here's a good web site that can explain how an alternator works along with the charge indicator light. Understanding Alternators, How Alternators Work

Hopefully after reading this link and a general understanding of the electrical circuit you'll be able to efficiently troubleshoot the situation. I'm not certain I'd dig into this until I had my hands on the wiring schematic.

Here is another thought... AutoZone and others offer free alternator testing. It might be a challenge for them to find the right set of pig tails to use for the test, but I'm nearly 90% confident the machine tests the diodes as part of its automated diagnostics. Perhaps this alternator size is used on a small import. I know it is a stretch.

 

[SnowRidgeME]

Got my service manual, the dynamo puts out the AC voltage per the manual, so quite sure my dynamo is OK. Looking at the voltage regulator, can anyone figure out what the manual is trying to dictate? What does the chart mean on the attached?

 

[Volfandt]

SnowRidgeME, the chart is giving the results you should get when you read the disconnected voltage regulator w/a multimeter.
If I read the chart correctly, (using the left column as a ref.) you should:
1) set the meter to read ohm's in the upper range, i.e. 1K, 10k or higher ohms.
2) disconnect the regulator so you can access the pins on the regulators connector.
3) place the meters + (red) lead on pin 1 and the - (black) lead on pin 5, you should read continuity. If it reads open the regulator is bad. It doesn't specify but lets assume for now that if you read any resistance that this step is good.
4) keeping the red lead on pin 1, move the black lead to pin 6, you should get the same reading as you did on pin 5.
5) skip pin 2
6) red lead on pin 3 and black led on pin 6 should read continuity. (same s previous tests).
-and so on.

Everytime I read electronics w/a multimeter, I'll switch the polarity of the meter's leads to make sure I'm not reading a dead short, so you'll want to do this at each step also. I say this because good diodes should only read continuity with the meters polarity set the correct way, in other words, it'll read good one way and open the other.

If the readings pass then it's safe to assume the regulator is good. If any one of the readings fail, the regulator can be assumed to be bad.


Good luck
Dave

 

[SnowRidgeME]

Conclusion: Bad Regulator, Dynamo checked out OK per spec, grounds and wire continuity was good, so I figured it had to be the voltage regulator, took it off, and it stank burnt electronics. New regulator part number is PN201-68562 for future reference. Thank you all for your help.