Battery light on at idle, off at 1,100 RPMs- a first for me

[casey lb1914]

Here is my problem and hoping someone had this issue and can point me in the right direction, I tried to start my Kioti LB1914 today after sitting for 3 months and had a dead battery I mean 0 volts dead, charged the battery and it started up fine, determined that the battery failed so bought a new one and installed it, started up fine and now my voltage light came on while at idle but as soon as I raised the speed past 1,100 RPMs the light goes off. So my first thought was I again have a bad alternator (replaced with new aftermarket in March) I put the multimeter on the battery and Iam getting 12.8 at 2000 RPMS which I believe should be around 14. so I tried the old trick of removing the negative battery cable while running ( at idle speed and at 2000 RPMS) if the alternator is bad the tractor should stall, while no luck it was still running. I'am not new to turning a wrench but i'am also not a pro, the two test don't make sense to me, so could it possible be the regulator? was the battery bad or was it drained? any ideas ? Is there any way to bench test a alternator? Thanks

 

[K5lwq]

Here is my problem and hoping someone had this issue and can point me in the right direction, I tried to start my Kioti LB1914 today after sitting for 3 months and had a dead battery I mean 0 volts dead, charged the battery and it started up fine, determined that the battery failed so bought a new one and installed it, started up fine and now my voltage light came on while at idle but as soon as I raised the speed past 1,100 RPMs the light goes off. So my first thought was I again have a bad alternator (replaced with new aftermarket in March) I put the multimeter on the battery and Iam getting 12.8 at 2000 RPMS which I believe should be around 14. so I tried the old trick of removing the negative battery cable while running ( at idle speed and at 2000 RPMS) if the alternator is bad the tractor should stall, while no luck it was still running. I'am not new to turning a wrench but i'am also not a pro, the two test don't make sense to me, so could it possible be the regulator? was the battery bad or was it drained? any ideas ? Is there any way to bench test a alternator? Thanks

First of all removing the ground will not kill your tractor because it is Diesel.

Sounds like the external voltage regulator is not working or something is unplugged. If you can, take it to a shop that rebuilds alternators and they can troubleshoot for you. Usually they will have a voltage regulator that will work.

 

[RickB]

First of all removing the ground will not kill your tractor because it is Diesel.

Sounds like the external voltage regulator is not working or something is unplugged. If you can, take it to a shop that rebuilds alternators and they can troubleshoot for you. Usually they will have a voltage regulator that will work.

Removing the battery ground while a machine equipped with an alternator is running is often detrimental to the alternator. Most qualified mechanics will not use that method.

 

[justman777]

Take the battery off and put it on a charger overnight. Every battery I've got from a big box store has been low on voltage. I've started asking them to test it with a multi-meter before I leave the store, and if it's below 12.4 volts, I ask for a fresher battery. 12.4 volts is typically close enough to dead that it starts harming the battery. They typically give you the oldest one they have in stock.

If tractors are like cars, you're not going to get 14 volts off the alternator until you turn on the headlights or some other high draw item. The high draw causes the ECM to demand more from the alternator to compensate for the electricity being used.

 

[RandyT]

Removing the battery ground while a machine equipped with an alternator is running is often detrimental to the alternator. Most qualified mechanics will not use that method.

The voltage spike from disconnecting the ground has also been known to cook a few ECM modules also.

 

[casey lb1914]

Thanks to all for your input its greatly appreciated, as for the old trick of pulling the negative off while running use to be standard practice in my neck of the woods. I recently have heard it could cause problems with the ECU in modern gas vehicles, what I wasn't aware of is that this method only applied to gas motors and I 'am finding diesels are a whole different animal, thanks for the info. My first step will be putting the battery on the charger in the morning and check the voltage with a load on and see what happens, If it doesn't work I'll have to find and alternator rebuild shop and have it tested. I'll keep you posted in hopes someone else may benefit from this. Thanks again to all

 

[ritcheyvs]

Disconnecting the alternator (or battery terminal) while the engine is running CAN zap a diode in the alternator. This only happens sometimes but don't do it.

You can probably get the alternator tested at most DIY auto parts places, like Autozone.

 

[RustyA]

Once your battery is fully charged test the battery voltage before starting the tractor. Then measure voltage at battery with tractor running a few minutes with lights on. Charging system may have a ramp-up program that takes a few minutes of load to reach full charging output. Under load with lights on it should show around 14.2 volts at battery. If not look for an external regulator in the engine compartment...that may be your culprit. Be sure to also check and clean the grounds from the battery to the frame.

 

[Kioti Paul]

I agree with all the advice that has been given so far. I am a little unclear if your voltage light has just now begun to remain lit (until 1,100 RPM), or did it maybe begin with the replacement alternator? If the "new" alternator has always acted this way, it is very likely just a 'quirk' of the particular alternator.

If it just began after finding the battery totally dead, it MIGHT be from a diode failing. Almost every time a diode fails, it fails "open"; (ie it will not conduct electricity in either 'direction) but occasionally they will fail "closed" (shorted). If that happens, it may just have a very slight 'leakage', which will drain the battery over a period of several days, or it could develop a 'dead short' which could be bad enough to burn out whatever device protects the alternator's battery wire.

It is pretty easy to check for shorted diodes. Just remove the battery wire from the alternator (the heavy wire, fastened with a stud and nut). Do this with the engine off; and be very careful, because this wire goes directly to the battery, and is ALWAYS "hot". Hold the multimeter's positive lead against the eyelet of the battery wire, and hold the negative lead against the stud on the alternator.

The meter should read zero volts. If it reads a few '100ths' of a volt, you can most likely consider that the same as zero (make sure the meter is not reading the voltage path through yourself, ie don't touch both probes with your hands). If the meter reads a few '10ths' of a volt or more, it is (almost) certain that there is enough leakage through the alternator to drain your battery over a day or two.

If the meter is reading zero, keep the positive lead on the wire, and touch the negative lead to a good ground. Confirm the meter reads battery voltage.

All that said, 12.8 volts at 2,000 RPM, is not unusual in your given situation. It is very likely the replacement battery was in a state of discharge, and while I am not familiar with the alternator on a LB1914, I would guess that it does not have a terribly high output, so if the battery was (somewhat) discharged, it might take several hours of running (at 2,000 RPM) to see the full output voltage. Even then, I don't think you will see 14 volts; more likely mid to upper 13's. (IMO)

Good Luck! Let us know what you find.

 

[RickB]

Reading 12.8 volts at the battery at 2000 ERPM is absolutely abnormal and a clear indication that something is wrong with the charging system or the wiring for that system.