OK, this ought to be an easy one, but the coffee hasn't soaked in very deep. I have a loader that is charging up a storm, (err, I mean normally, about 13.9 VDC). Problem is the charge indicator light is on. This has a Delco reman pn TY6775 alternator. There is proper voltage at the alternator B+ and at the battery, but the light stays on. I don't have the schematic so I can't see which of the other three terminals either supplies the light, or grounds it. Oh, and this is the 4 wire alternator. Connections appear shaky, but wiggle test has no effect on light. Anyone have a quick simple answer? I don't, at the moment anyway.
TRADITIONALLY, the excite voltage came from the ignition switch, through the alternator warning light, and to the excite terminal on the alternator. If the wire broke, the light burned out, etc. then the light would not light obviously, but the alternator would not charge either. Hence, you check the light to see if it comes on when you turn the key, before starting. Obviously your light is functioning if it lights up while running. Unless it's shorted somewhere in addition to the supplying the excite voltage. Simple answer, the alternator is weak and not fully exciting itself so the current keeps flowing and the light does not go out. What happens if you turn all the accessories on at half engine speed?
Delmer, thanks for the reply. I’ll have to get back to you on that. Got pulled onto another machine. I’ll post back ASAP on that test.
This may be a problem with a bad relay. On my JD backhoe, if the auxiliary relay doesn't close the charge light is on and the hour meter doesn't change.
JL, I’ll check that too as soon as I get back on it. Trying to outthink a 6 speed Allison in a F750 first. Thank you!
My opinion, I think 13.9 or less is not enough to turn out the light. You should have a good 14.5 volt's. The voltage regulator in the alt is probably going, or a bad connection somewhere. Most likely the regulator inside the alt.
This might help. The JD TY6775 is a Delco 10si 76 amp unit. The indicator circuit with warning light, may simply have a bad connection. You could easily bypass (to test) the indicator circuit with your test light. Go from terminal 1 to battery and your test light should stay off. Or, like Hookedondiesel suggested, your vr may be faulty. There is a test tab on the back of the unit that allows you to full field the alternator and bypass the VR. The voltage should jump to about 14.7v when you do that. If your circuit for 1 and 2 is correct, (no bad connections) and you have a load on the system, 13.9v is a bit low. You could have 1 bad diode in the rectifier.
I took a little time to go back to this machine, but just a little. The output of the alternator is pretty steady, even when turning on the limited accessories. This machine doesn't have many. As usual, the voltage drops for a second or two when switching on the accessories, but comes back, so that tells me the VR is probably doing its job. 13.9 is maybe a little low, but part of that is determined by the state of charge of the battery, which in this case is brand new. If no charge is needed, the VR should trim the alternator input down to avoid overcharging or drying out the battery. My suspicions are that the light should be on only if one side of it is more negative than the other, showing that there is actual current flow in a certain direction. Usually a diode controls which way the current flowing make the light come on. As long as the battery is charging, the current balance causes the light to go out since the current is flowing into the battery rather than from it. If the engine and systems are running from the battery, as in the case of an low current from the alternator, the flow is reversed and the diode allow the light to come on. But if there are relays involved, then it's possible they are faulty or poorly connected, and there could be a leaky diode somewhere. I can and will check all of that. I also have a good starter/alternator shop I can take the alternator to for load testing. I'll put a scope on the output, which will show a bad diode in the rectifier bridge. I can also ground the test tab and see if the voltage comes up. Kind of have my doubts there, but since it's such an easy test, why not... I've run this machine under accessory load for several hours without depleting the battery, and the alternator output remains a steady 13.9. I don't really see a problem with that. I feel the problem is in the wiring surrounding the indicator light. Coaldust, thank you for that diagram. It will help me pick my test points.
Does the light come on every time? Or does it come on only sometimes?
It's constantly on when running. Engine speed nor load affect it.
Keep us posted.
By all means! We have poor weather for the next few days, so I don't expect to spend any time on it for a bit, but I will post my findings.
You're overthinking things in post #8. The light turns on and off based on current flow like you say. A diode is used instead of a warning light on some wiring diagrams for gas engines, in order to keep the excite circuit from "backfeeding" the ignition circuit and keeping the engine running even with the key off. I'm thinking the issue is going to be close to the warning light wiring, but not that circuit itself. That is it will be an alternator problem, or alternator to battery problem, or else it will be an issue with something else on that ignition circuit like a poor connection at the ignition switch and the alternator backfeeding to "help out" that circuit. Maybe a ground somewhere, but I can't think of where.
Delmer, Yes. There is much overthinking going on. Especially, talking about a 50 year old Delco 10si. The simplest and purest alternator and charging circuit ever designed. One of the first transistorized circuits ever used on a car, except for the AM/FM radio. But, when this alternator hit the market, FM was still an option. Paid extra for that. But, why not? It’s fun anyways. Pulling the scope out, looking at some wave forms. We are going all in on this one. Whatever it takes to turn that red indicator lamp off. We’ll get er’ figured out
Serial number? Check your alternator relay. That controls the light in your instrument panel.
Try jumping alt power to excite lug on alt and see if charging output goes up. I think I remember a 544 not charging until you revved the engine up but that may have had a week alternator we had to replace a few months later. I have a deere alt in shop now probably same vintage on a gen set. It will slowly go up to 14.5 but hangs at 13.7 for a bit.
Tony, you asked for a quick simple answer, here it is....swap the alt.
BBBut that may end the discussion ! mg2361's info about the relay is one thing in the circuit that a not many people are aware of. I don't know how he remembers all of the technical info he posts.
As long as it stays above 13.5 with all the loads on (lights, blower, etc) I wouldn't worry about the charging voltage. 13.9V is just fine.
Yabbut that takes all the fun out of it. Especially if the problem is a silly bad connection. Feel like I ought to at least check that stuff first. And mg , I said a little low, not condemnably low....I would like to see it higher, but I'll take the 13.9. And I believe that should be enough to extinguish the light, so I'm not itching to replace the alternator just yet. And for the record, overthinking is one of my most outstanding failings when it comes to some things. Maybe that paints me a fatalist, or maybe a victim of "paralysis by analysis", but I freely admit this. Of course, most of the (over)thinking is when I'm away from the machine at home on the sofa or something. At the machine, I poke, probe, prod and test everything I can get to, looking for the problem. And I do appreciate all the comments, recommendations and suggestions from you guys. I recognize that most all of you have more time in trade than I do when it comes to heavy equipment, but as a general wrench, I'm not exactly new. Made by first official greasy dollar rebuilding 4 straight six Chev's in a friend's work fleet when I was just 10.
You said it is a new rebuild alternator? Check and see if it self excites after disconnecting the plug, Just had a similar situation on a 2090 Case ag tractor that had the 10SI 3 wire alternator on it, with the SE alternator on and the plug in hooked up it the charge light would be lit constantly and the unit would work and charge normally, the solution for this farmer was to let the charge light/ exciter wire disconnected. See if it starts and charges normally hooked up 1 wire, If the light goes out when the plug is disconnected shut off look at the alternator, don't over complicate things do the simple stuff first
melben, this is not a new rebuild as in I just installed it. The tag is dated 9/25/93, so it easily could have many hours on it. This one has the three wire aux plug, which I understand less about than the typical 2 wire aux. All of the terminals are a little loose, so first thing is to remove them from the plastic plug, deox them and bend them tight again. And deox the male side on the alternator itself. Some have mentioned a relay being involved here. Anyone point out the physical location of it? I'm not there, and won't be for a few days. We have unusually cold and snowy conditions here this week. Supposed to be 0° tonight and we have 8" snow on the ground. Us Texans ain't used to that. I don't plan on leaving my place for a day or three.
my advice still stands for diagnosis, yes i thought it was a new rebuild but if the light goes out when the plug is unplugged something in the alternator is giving the dash light a path to ground. A others have stated, the light is turned off by voltage equalization, not by a physical switch.
You most likely have a bad diode.
Of course some of this information is serial number dependent so serial number would help with accurate information. If your serial number is over 518774 then there may not be a relay. Going back to post #15, if the alternator relay is bad your alternator will still charge the battery, the alternator can still "try" to control the light (for lack of a better description), but if the alternator relay is not doing it's job the light on the panel will stay lit. The relay is "wired" in between the alternator and the light (on most 544E's).
Awesome info. mg2361. Not many (me included) would have ever thought that relay would or could be in a charging circuit. Did JD put them in very many machines ? Like excavators and the agricultural line of equipment. I have never even (ever) read about them in all the time I have been on HEF.
I have no idea about the AG end, but no, not many machines had that relay that I can recall. Some of the wheel loaders of that vintage (not even all the "E" series had them) and I think the old 690E excavators. There are probably others, but I'm not sure. My memory is fading.......
edgephoto , just for kicks, I will put a scope to the alternator output to see if the waveform shows a diode out in the main rectifier bridge. These are 3 phase alternators I believe, so it should show easily. Otherwise I can pull the alternator and check each individually. Back in the old days, we used to replace diodes when they went bad. We didn't automatically replace the entire alternator. I still have a local repair shop I should be able to buy parts from if it comes to that. mg thanks for that diagram. I'll check and bypass that relay (provided it is used on this machine) if nothing else simple shows up.. It's a good possibility. This machine has been sitting idle (bad trans) for 3-4 years so nothing will surprise me. I don't have the SN here, but in my notebook which I left in it. I'll get it when I go back to the shop. Thanks all! Several troubleshooting tips have been presented, and appreciated.
If it is a 10si alternator I would just replace the rectifier bridge myself. I would not replace the whole alternator.
AC Ripple should not exceed 500mV at 1500 rpm with lights and accessories on.
I agree, and of course, could put an external diode/rectifier as a bandaid, but I'm not too keen on that approach. I'd replace the bridge first.
I agree, while your at it, replace the voltage regulator....and make sure your scope is calibrated properly, (OOT). Hopefully you've checked your negative and positive cable's for resistance,...and voltage drop's, what am I thinking, of course you have. I'm wondering if the ozone may have some effect on your dilemma. Perhaps alternator belt integrity or tire pressure. Who know's...In any event, please let us know what you deduce.
Ok, back to this for a little while. This is my relay board. Naturally no labels of any sort and no documentation. So I have to trace the charge circuit down to see which relay controls the light, assuming this one even uses a relay. Sure wish it wasn’t so tough for us aftermarket guys to get paperwork on stuff like this. The OEM’s have to know there are a bunch of us out here, and bring a free economy, we’re not going anywhere. And in cases like this, surely there aren’t so many units being worked on that the failure to call out a dealer tech would really cost them. Just a control issue to keep just anyone from working on this stuff and making mistakes that could cost lots of money, damage and loss of life or limb that in today’s world would end up being a lawsuit I suppose. Plenty of hungry, less that scrupulous lawyers out there. Maybe I should call Saul.
mg2361, thank you for that. This is my main Monday project. You'll also notice a very wet pan under all of this. There is a short hydraulic hose that has a pretty steady leak that I want to replace before I start digging around too much in there, but hopefully the colors/numbers are still legible. Overall this machine is pretty rough and needs some body work, including a new windsheild. Lots of bent up stuff from operators running over things or turning into other machines or trees. We seem to have a problem with some of the trackhoe operators swinging around and clobbering whatever is in the way. But I'm trying to get this one running right at least, and then we have a good fab guy who will straighten or replace the bent stuff, and we seem to have enough work to keep a sandblast and paint guy pretty busy. In the end, it will be a decent machine.
mg2361, in your lower left circle, the relay has these wires: m06 and m06B purple G10A and G10B Blk J01 and J02F Tan That's as close to what you described as I could locate. Nothing close in the other circled items. Other than the J01F you referred to, this looks close to the circuit you wanted to find. All I have is J01, or J02F Worked in my building today, but let the welders bring a dump trailer (yes, the single hose trailer!) so the could work out of the rain and put some new side plates on. They're going split the single hung end door tomorrow. So there will be two days where the fumes will be some bothersome, besides my own as I try to get a 07 International 8600 cranked. No keys, so spent time today swapping out lock cylinders so I now have keys at least, So, what can you tell me about that relay?
That would be the alternator relay. I PM'd you.
As soon as I get the hosing sorted out and repack a cylinder, I'll be able to run it and see where the current drops out. Or if that relay is bad. I'll post what I find. Thanks mg, I appreciate the assist. Looks pretty straightforward. Figured it would be, but following the butchers I never know. I don't think this circuit has been tampered with, so it should be simple. And for all those saying it's the alternator, It could be. Just have to do some poking around with a meter, now that I know what I'm looking at. I don't like guessing...it leads to assuming all too often. t This is after I get new batteries on a 07 Int'l 8600 that has lost keys. It's in the way, a nice truck, and we need to put it to work or for sale. But I started that project yesterday, so may try to knock it out today.
Well once again this project got sidelined. Our Volvo 460 hoe caught fire today. I'll be spending a few days evaluating the damage and making a plan to repair it. The fire started at the feed thru on the head where the injector control harness goes in. Fortunately, the operator noticed it and within a minute or so was on it with the fire extinguisher and minimized the damage. I have another Volvo sitting where it burned from some welders and a lot of oil accumulation. That on may get parted out. The 460, we just put an engine in last year. I may start a thread for posterity's sake on how this goes. It seems a lot of my projects get "rescheduled" just to help keep operations going. Never a dull moment.