I have a Kubota in my skid steer. The alternator was replaced with a 2 wire Leece Neville. The charge light always stayed bright when first started but once revved up would go out and stay off if brought back to idle. I was fine with this and figured the alternator just needed a little extra speed to kick in. Today I noticed the light stayed on at all speeds but was dim and not nearly as bright as when you turn the key on or first start the machine. It was at the end of the day and I didn't have time to check anything. Wondering what would cause the charging light to stay on but be dim? Was reading it could be from loose or corroded battery terminals. Could batteries going bad cause it? It's easy enough to check the battery connections if I take the seat out but wondering if a diode went bad in the alternator and I should take it in to get checked? Any other things to check?
I would check the voltage drop from the alternator to the battery post, and the ground side also. If those are fine, like less than .1V difference after it's run for a bit and the battery should be charged back up from starting, then ignore the light. As long as it charges correctly, and the battery doesn't drain over night, then everything is working fine.
I'd get the diodes checked, my personal experience is the fault you're describing was always a faulty diode in the alternator.
I'll do some checks when I go back out.
From what I know 1 bad diode out of 6 diodes will give you 1/3 output at full rpm. You can also test for AC Current from the positive output of alternator to the positive of the battery with multimeter on AC volts selection. Over 500mv or basically 1/2 a volt tells you the diodes are not doing there job in changing the AC to DC current. Hope it helps. Simon C
I was reading to check for AC voltage as it indicates a bad diode. Maybe I'll get lucky and just have to clean the battery connections. It's almost like the charging light is trying to go out and flickering a little.
I did some checking today. When first started the light is full brightness. After I let the machine warm up I increased the throttle and the light went out. I checked volts right at the alternator and it was 14.55. After about a minute the light came on really dim. I shut the machine off and started it again and the light was off. I shut it off again and took the seat out to get to the batteries. There was no corrosion or anything out of the ordinary. I started the machine but it had cooled off enough I had to crank it for 5 or 6 seconds and I didn't use the glow plugs. Initial start needs the glow plugs. I checked voltage and had 14.35 volts at idle and 14.23 when revved up. I checked for AC volts but apparently multimeters don't zero for AC volts. On the 20 volt setting after a few seconds got .03 AC volts. I loosened a couple battery clamps and turned them a little and tightened them back up. The charge light stayed off the whole time I was checking at the batteries. I left the machine running for about 15 minutes and the light stayed completely off. I'm thinking maybe something in the voltage regulator was a little stuck or the light only goes very dim when the battery is at maximum charge. The little bit of extra cranking was enough to require the battery needed charging. It seemed odd I couldn't get the light to come back on dim after 15 minutes but leads to think there's not really a problem that needs attention. The very dim light just means the battery is at maximum charge. I'll monitor it and see if anything changes.
the alternator has to excite so revving it up may be necessary was the alternator you installed intended for a diesel engine? and did it have the same size pulley as what you replaced? what is your low idle speed set at? possibly it too low.....no fully charged battery's don't put the charge lamp on. a machine uses the alternator to operate its electrical functions while running. the battery's for starting and back up when machine is not running if the dim glowing lamp bothers you dig deeper if not I don't think its worth worrying about. another thing that can cause that is a wrong charge lamp bulb the voltages has to equal out on both sides of the bulb so it doesn't light
if you are experiencing a dead battery as well then I would have the alternator checked for a bad diode
The alternator was replaced by an experienced auto electric shop about 6 or 7 years ago. I didn't have any issues with having to rev the engine up to get the alternator charging. Once I rev the engine to turn the light off I can bring it back to idle and it charges. I always let the machine warm up first though. It's a skid steer so it's generally run at full throttle. I realize the charging light isn't suppsed to come on because the battery is fully charged but that appears to be what is happening. There's nothing wrong with the lamp and there was never a dead battery. If you read my last post I mentioned that I don't think it's anything to worry about but I will monitor it.
right on....electrical problems cam be so funky and weird!! some never seem to make sense!!
Especially when they're intermittent. Electrical troubleshooting on vehicles isn't one of my stronger suits. I think I share that with quite a few others.
Tested a friends car for stray AC voltage from the Positive post of alternator to the positive post of battery. As she revved up the car to 1500 RPM, with no load she started to put fan on, Rear defog on and all lights on. The highest reading with alternator putting out lots of current was 0.065 amps or said otherwise 65 milliamps of AC current showing that her diodes were doing there job well. Most cars with good alternators put out less than 100 milliamps of AC current when under load. 500 is the number that says need new parts. Hope it helps. Simon C
I wanted to update this thread. I've had to boost the skid steer the last 2 times I used it. It appears that although the batteries seem good, they just don't have enough power to energize the solenoid. Boosting is no issue. Maybe the glow plugs take enough power out of the batteries?? Now I'm wondering if the batteries could be going bad and it's also what caused the flickering charging light?
Some batteries suck so much amperage because of sulphated plates that the alternator can hardly keep up with the charge at lower RPM's. For those that don't know it, an alternator with a 6 Diode rectifier will still produce 33% of the maximum amps with 1 diode burn't. That is when a person who uses too many accessories for the limited output of the failing alternator will have a no start one day. This is further aggravated by a partially sulphated battery. Also we sometimes forget that at minus 18c or 0F a perfect battery will have less than 30 percent capacity for starting. A 1/2 worn out battery will have even less capacity. It's the reason why at 80F you can start your vehicle probably 10-20 times. Try that at minus 40C and fortunate to get 3 tries. Hook both test leads of a meter to the center of the battery posts and have someone try to start it, record how far the battery goes down and what temperature it was in the morning and I can tell you from a chart I have what your battery conditoon is. Battery nees to be fully charged the night before. Would also be good to do the test I specified above in post#13 to check your alternators diode state while the motor is revved and lights on. Any questions, fire away. Simon C
A simple test for bad diodes. All you need is a 12 volt test light. Disconnect the alternator output cable. If you connect the test light between the output post of the alternator and the disconnected cable and the test light comes on, you have at least one bad diode. This condition will also cause a battery to lose it's charge in a short amount of time. Obviously the battery must be charged for this test.
Coming back to revive this thread. After new glow plugs, key switch and a relay on the starting circuit the skid steer is starting and running great. Seems to spin over with the relay added too. The charging light would come dim but only occasionally. Batteries never drained at all. After using the machine for a few hours I noticed the fuel gauge was staying on full. I didn't have much time to test things because it was getting dark. I did notice the gauge goes to full when the key is turned on but not started. Interestingly when running the gauge appeared to read about 5/8 full (maybe accurate) if I turned the key off when running. The needle on the gauge did fluctuate a bit if I jerked the machine back and forth. I'm wondering if the dim light and fuel gauge issues could be related? Maybe there is a bad diode in the alternator or something else making things go wonky? Turning the lights and heater on made no difference to the dim charge light. The dim light doesn't come on right away. Only seems to come on after running for awhile. Also wondering if the sending unit could be bad. A random test on the 2 posts showed 14.7 ohms which I took to mean it's not shorted and is doing something. It's very frustrating. I tried cleaning all the wire connections on the sender and fuel gauge. Note of caution: Don't use Lloyd's electrical contact cleaner on plastic. It says suitable for most plastics but caused the plastic mounting on the fuel gauge to crack and fall apart. I was able to tighten the nuts and put some RTV silicone on the gauge to hold it in place.
Thanks for the info on electrical contact cleaner, Good to know. I once put a drop of loctite on a head lamp that I had, and it was I guess the wrong kind of plastic and just melted the plastic next to the nut. Simon C
Apparently not all electrical contact cleaners affect plastic but the Lloyd's sure did.