My tractor was running fine most of the summer. One day it started losing power and died. Got it jump started and got it close enough to the house to where I can closely look at it. Got the battery tested at NAPA and they said it is completely shot. Got a new battery and installed it yesterday. As it sits in the tractor with everything off I'm at 12.7v, with it running I'm still at 12.7v. I remember searching through the threads awhile ago and vaguely remember that with a good alternator I should be getting at least 13+v with the tractor running. I cant seem to find this information right now. Does this sound correct? All of my connections are tight and clean. I have a L245DT. I have a box in the gauge cluster that I think is the voltage regulator/dynamo? Could this be bad also? Or both? The "charge" light in the gauge hasn't worked in years and most likely burnt out. Thanks.
Bad alternator? What do you guys think?
- Thread starter NWHmoob
- Start date
85Hokie
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You are correct.
This part of the story is strange, on a typical diesel you only need the battery to start, after that the battery does nothing for running. However, some use a battery to keep fuel flowing, so that might what shut you down.
Battery sitting is 12.6+ and charging should be close to 14v
IF YOU are NOT getting a charge, one of two places to look, the alternator is one and the rectifier is the other. You machine has both separate I believe.
YOU can remove the alternator if it has one, not sure of your model - might have a dyno. Both can be tested.
you have a picture you can upload and that will help determine what to do next
Daren Todd
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You will need to check voltage at the alternator. On the big post, you should be reading battery voltage. Then with key on, but not started, you should be getting battery voltage to one of the small wires going to the alternator. The small wire is the exciter wire which tells the alternator to charge. If your not getting power to one of the small wires, check your fuses.
If fuse is good, then check your wiring going to alternator. Could be a bum wire.
If your getting power to both the big post and small wire, Then the issue is with your alternator.
With engine running, you should be seeing between 13.5 and 14.2 volts at the big post on the alternator.
If fuse is good, then check your wiring going to alternator. Could be a bum wire.
If your getting power to both the big post and small wire, Then the issue is with your alternator.
With engine running, you should be seeing between 13.5 and 14.2 volts at the big post on the alternator.
Check your lamp/bulb and test it with 12 volts, if it is blown, replace it with the same bulb, same wattage, it's part of the charging circuit an generally supplies initial excitation of the alternator.
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I'm supposing you checked the running voltage at something more than an idle. I know on my M4500 it won't start charging until after the engine goes past 15-1700 the first time (it'll then charge even at idle after that).
rbargeron
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After the engine starts, running voltage is usually up near 14 but it cuts back as it runs. It also fluctuates with lights and other loads switched on. If the regulator is working the voltage should stay above 12 while running, occasionally being as high as 15. Anything above 12.6 definitely indicates a working alternator.
So I checked the alternator with it running yesterday. I'm getting 12.6 at the large post and there is a 3 pin connector. On the "E" and "F" I'm getting 0v and "N" I'm getting 0.12V. Also with the lights on voltage drops to 12.5v.
No I have not checked voltage at other RPM besides idle.
Here's what mine looks like.
No I have not checked voltage at other RPM besides idle.
Here's what mine looks like.
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Did you check the bulb? As previously mentioned, it provides initial excitation to the rotor, (to magnetize the rotor) so the alternator can start outputting power, once it excites itself, the regulator takes over the control. Yours "could" be as simple as this bulb, it may not, but it's worth the check.
First, you want to see a minimum of 13.5 volts, this is the bottom of acceptable. The 12.6V you are seeing is just the battery voltage, about right for a charged 12V battery.
The letters F, N and E are field, neutral and earth. This indicated you have a remote regulator. The bolt on wire should have battery voltage. The F is the field current and is controlled by the regulator. The N terminal will produce current in the form of half wave rectified and it comes from the "WYE" connection at the stator. This can be used to either run a relay in the regulator that turns out a charge lamp when its charging, it can also be used to run an hour meter as it only produces when the engine is running (assuming charging system is working) and the F is field and this is what we call a "B" circuit, meaning other side of field is grounded inside the alternator so the regulator supplys voltage to this based on the regulator. This is how charging is throttled back. The E terminal is just a ground. The F, N and E will run to the regulator. There will be a few more at the regulator, a 12V, 12V with key. Here is a nice little test. When its running, lightly tap on the rear frame (SRE or slip ring end) with a hammer near the connector. If the brushes are worn down, this will (((shake))) a little more length and it will start to work if it is worn brushes (not a fix, just a check, if ti works, then solder in new brushes).
My cousin had a 1978 L185, no charge, he sent me the alternator, brushes were fine. He checked all connectors (pin checks), all good, replaced the regulator and all was fine.
The "bulb check" is only used on internal regulated charging systems with a diode trio, this supplied voltage via the bulb circuit does excite the alternator, than the diode trio produces a counter voltage that cancels out the light, but with your F, N and E terminals, this system wont apply to you.
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Whilst I don't have his tractor or diagram in front of me to determine exactly what he has, he may as well check and fix his bulb as it's a hell of a lot easier watching the bulb come on and go out every time he starts his tractor, than getting out a multimeter each time. I realize the regulator may be at fault, and it could be the cause of the bulb not working, but one has to start somewhere to get some testing and results as generally the OP's aren't qualified auto electricians, otherwise they wouldn't be asking the questions.
Some externally regulated alternator systems used the bulb in the excitation circuit, but I'll take your word that Kubota hasn't.
Great to have some extra experience on the board, just may need to pitch some info a bit lower. YMMV
YMMV.
Yes, I always like a lamp, I dont always see a gauge when working, a lamp gets your attention. Gauges are great, but I'd rather have both IMHO.
Yes, there is a system, the terminals on the alternator will usually be labeled E L F or earth, light and field (Nippondenso or any MFG from Japan) . The "L" or light circuit is the counter voltage from the trio. The light circuit tickles it, and the trio provides the counter voltage and field current (excited) after its initialized.
This system, the field is an "A" circuit, where as the regulator controls the ground and the other side of the field is powered by the diode trio, in addition to canceling out the light via the counter voltage. To determine if field is an "A" or a "B" circuit, I used this tidbit of info. In a "B" circuit, the regulator is BEFORE the field, while in an A circuit, the regulator is AFTER the field. In an A circuit, it controls the ground (other side is powered by battery), B circuit, it controls the battery. In a B circuit, one side of the brushes (field) will be grounded, in an An circuit, both sides will be insulated.
Most systems that use the light and trio counter voltage almost all use a A circuit. When I say field, I am referring to the rotor.
Thanks for the compliment 100TD, I worked as an alternator rebuilder for HD equipment, marine equipment, but did all automotive too. Smallest was a 10 amp alternator from a tractor, the biggest was an oil cooled 380 amp oil cooled greyhound bus, was gear driven from the crankshaft. I did starters also. I know way more about charging systems than anyone ever needs to know. It just came with the job and I valued those 4 years (85-89) I did it, wonderful learnign experience. Not much use for it now. But havent done that work for 29 yrs. I have been a Toyota dealer tech, same store for the last 29 yrs.
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I took the time to find a manual on Kubotabooks.com which has a wiring diagram.
Darren Todd suggested a check of fuses but I never read this was done.
On the wiring diagram, which is not the most legible I have seen, there appears to be a 10 amp fuse associated in some way with a wire to the voltage regulator. It is late here and I have not checked if the connection to the fuse is on the line or load side.
I would feel better if the owner used a test light to confirm all fuses are good.
Dave M7040
Darren Todd suggested a check of fuses but I never read this was done.
On the wiring diagram, which is not the most legible I have seen, there appears to be a 10 amp fuse associated in some way with a wire to the voltage regulator. It is late here and I have not checked if the connection to the fuse is on the line or load side.
I would feel better if the owner used a test light to confirm all fuses are good.
Dave M7040
Just doesn't make sense that the light on the gauge could be part of the issue as it has not been working for a number of years. With that said I've replaced the light with an led and it stays constantly lit. Now that I've got to replacing the gauge lights I also replaced my Oil Pressure light and now that one stays lit as well. Thanks to everyone for all the technical knowledge and inputs but I'm still not comprehending what you guys are saying. You guys need to dumb it down a little for me please so I can understand.
So........do I have a bad alternator or no?
Should I have used a halogen bulb instead of an led?
Forgot the check the amperage on the fuse as I was replacing the lights. Will do that when I get home.
Yes, the schematic is not legible in terms of letters or numbers.
So........do I have a bad alternator or no?
Should I have used a halogen bulb instead of an led?
Forgot the check the amperage on the fuse as I was replacing the lights. Will do that when I get home.
Yes, the schematic is not legible in terms of letters or numbers.
You can wire a resistor parallel with it. You can use just a diode too. The whole idea on that system is the diode trio, you excite the alternator with the small current going through the bulb, then the trio when the alternator is excited (producing its own field current) produces a counter voltage which cancels the light (opposing voltages cancel each other out). You don't really need a light bulb, you can use a plain old diode (also called a rectifier) wired inline, just make sure the striped end (cathode) of the diode points towards the alternator. The counter voltage will still flow back, but it stopped by the diode itself, where the light circuit would just knock the voltage down (light is a load) to where it wont do anything. Otherwise on a gas rig, the trio would power the ignition system up and you wouldn't be able to shut the engine off (trying to charge the battery via this circuit) and this would kill the trio in short order because it cant handle this load.
A diode itself, LED or otherwise is a direct short in one direction, so an LED cant be used as a bulb. But in this case, it could as there is the field that that ground path goes through which is a 4 ohm resistor. Otherwise, if you want to use a LED as a bulb, ie power to one side, ground to the other, you have to add a resistor inline (not parallel) unless you are dealing with millivolts. Many LED's for cars designed to replace a incandescent bulb has a resistor (load) built into it.
I know this is way more information than many need, but figured it would be useful to many in here. Pretty sharp group in this forum I have found.
If it does use the bulb ground current to excite it, it could work for years with a bad bulb. The alternator rotor has residual magnetism in it and with a little throttling up, will be enough to tickle the stator to produce current and (((boom))) then it now is producing its own current (charging) and did this with the open exciter circuit (burnt out bulb). But most Japanese mfg use a redundant system, ie a bulb, plus an IG (12V keyed to excite the alternator. The IG or 12V keyed circuit has a built in diode to prevent the feedback from the trio. This was done to allow the alt to work if there was a bulb failure
Sorry if I am getting boring.
***UPDATE***
I haven't done anything since last fall but have since replaced the battery, alternator, and voltage regulator in the last 2 weeks. With the battery just sitting there it's reading 12.6v, idle = 12.5v, full throttle = 12.5v. I have ran the tractor every other day for at least an hour or two doing some yard work taking advantage of the moment before something happens. It doesn't seem to be draining the battery like I expected but then again it doesn't seem like it's charging it either. Confused!
At this point it wouldn't hurt to try the light bulb! Any automotive 12v halogen will work I assume? Finding the original bulbs for these are few and far and expensive.
I haven't done anything since last fall but have since replaced the battery, alternator, and voltage regulator in the last 2 weeks. With the battery just sitting there it's reading 12.6v, idle = 12.5v, full throttle = 12.5v. I have ran the tractor every other day for at least an hour or two doing some yard work taking advantage of the moment before something happens. It doesn't seem to be draining the battery like I expected but then again it doesn't seem like it's charging it either. Confused!
At this point it wouldn't hurt to try the light bulb! Any automotive 12v halogen will work I assume? Finding the original bulbs for these are few and far and expensive.
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Daren Todd
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Check your 3 wires on the quick connect to the alternator. You should be getting 12 volt power to at least one of those wires to tell the alternator to start charging. If you don't have 12 volts going to it, the alternator will not generate power.
Power comes from the fuses to that point. If your not getting power, then you need to trace those wires back to the fuse panel and see why you aren't getting power
When checking voltage at the battery to see if it's charging, run your RPMS up to at least 1500. The alternator on my L1501 won't generate voltage until it's spinning at around 1300 rpms. Checking at an idle, all it reads is the current battery voltage. Running it up to 1500 rpms and checking it shows between 13.6 and 14.2 volts.
Depending on how your battery cables are and the condition of the connectors for the wires, you may only see a small jump of the voltage over time instead of reading 14 volts. For example, initial reading is 12.1 volts. Check it a minute later, it reads 12.3 volts. A few minutes later it may read 12.8 volts and slowly creep up to 14 volts over 15 minutes or so.
Also your tractor is a very simple system and only requires voltage to start it and run the lights. After it's started, the engine it self requires no voltage to stay running, and will continue to run till it's out of fuel or you shut it down.
Power comes from the fuses to that point. If your not getting power, then you need to trace those wires back to the fuse panel and see why you aren't getting power
When checking voltage at the battery to see if it's charging, run your RPMS up to at least 1500. The alternator on my L1501 won't generate voltage until it's spinning at around 1300 rpms. Checking at an idle, all it reads is the current battery voltage. Running it up to 1500 rpms and checking it shows between 13.6 and 14.2 volts.
Depending on how your battery cables are and the condition of the connectors for the wires, you may only see a small jump of the voltage over time instead of reading 14 volts. For example, initial reading is 12.1 volts. Check it a minute later, it reads 12.3 volts. A few minutes later it may read 12.8 volts and slowly creep up to 14 volts over 15 minutes or so.
Also your tractor is a very simple system and only requires voltage to start it and run the lights. After it's started, the engine it self requires no voltage to stay running, and will continue to run till it's out of fuel or you shut it down.
It would be great if someone could tell us what type bulb should be there I can’t find any information on where or what the part number is for the bulb