My alternator is not charging. So, a little background on what was going on and what happened. On my 299d xhp battery was old and the colder weather was killing it so i bought new battery and installed it. prior to the install the alternator was charging i was seeing approx.14V on the screen. I installed new batter started the cat up and now only showing 12.2V and of course it drops the longer the unit is running because not charging. I put another alternator on the unit had same issue so took it back and put the old one back on. I have checked all fuses inside cab all good. do not know if there are fuses somewhere else, I need to check. The wires on the back of the alternator i have the main wire going to the battery have a plug with a white wire in it and a single plug which is a green wire. With the switch on I get about the same voltage on the white wire as I have on the battery, I do not get any voltage on the green wire. If someone could help me out it would be great.
CAT 299D xhp vin number CAT0299DAJST01268
Did you check voltage output right at alternator terminal? White wire is voltage sense wire, it controls output of alternator based on load. Its correct to have 12v on it with key on. I think Green wire is field excitation wire, it gets alternator to start charging. But it could also be for tach. If its for the field excitation, it should have 12v. Do you have a tach? You could have got a crappy rebuilt alternator, its common. Hopefully someone will be along and decipher your serial number.
Alternator wiring.
I stand corrected, Thanks Nige,
Sounds like your wiring checks out. You probably got a bad rebuild. That, or your excite wire is compromised, (green crusties), and is failing under load.
How about 3 simple test with multimeter: #1- With Engine running and revved up 1/2 throttle and Lights on and Heater Fan on Stab the Red Output post of Alternator with RED test lead. Stab the dead center of the Positive post of battery with the Black test lead. Any reading over 0.5 volts means cable is compromised. #2 Same engine running stab the Side of the Alternator Steel Case on clean steel with the RED meter lead, and the BLACK test lead on the dead center of the Battery Negative terminal. Any reading over 0.5 volts DC indicates a compromised negative cable from Engine Block to frame back to battery. If you have a master disconnect switch it has to be on obviously. If the number is higher than 0.5 Volts DC put your meter leads on the master disconnect switch if you have one ( one test lead on each stud ) . What does that small test reveal ? #3 Same engine running while revved and loaded up with fan and lights stab the R-Terminal of the alternator where the white wire goes in with your Red Meter lead and Stab the Dead center of the Negative post of your battery with the Black meter lead. What does it read. Start with these three tests to eliminate bad cables under load. They can test perfect with no load and fail under load. Simon C
do have a RMP (tach) but i was told that the green wire should have 12 volts to start the alternator to start but do not have it. don't know where it comes from in the system. Also, I did check at the alternator and still nothing.
According to diagram, field is controlled by white wire, R terminal. Tach is driven off off P terminal. You have your 12v at R, however, that does not have any load on it. You need to verify the integrity of that wire under load. If it’s impossible to access terminals with alternator in place and running, remove alt. and connect a 12v bulb (2-3amp) in series to white wire. Ground one side of bulb and turn on key, if bulb stays lit, you’re good to go. If it goes dim or goes out, you have a bad wire somewhere in harness.
Very good test to do to eliminate whether the computer is sending the signal consistently without dropping out because of a poor connection somewhere. Wanted to say that owner said all the non-charging started after he changed the battery, makes me wonder if something happened to one of the connections in there while manhandling the battery out of the compartment. If he checks all we have suggested, something will come up as a weakness. Simon C
Unfortunately that information is incorrect. The wire 403 GN to the alternator is not used in your particular machine application. The wire goes from the alternator into one side of the first major (31-pin) harness connector after the alternator but there is no corresponding wire coming out of the other side of that connector, instead there is only a blank hole. I would imagine the harness is a "standard" one and it was easier to leave the wire in there than it was to build a different one without the green wire using a different Part Number.
Nice of Cat to add confusion, with phantom wires that lead no where. Where is tach signal pulled from?
Engine ECM - crank speed sensor.
Ok I was able to perform 2 of the three test you ask the third one i am goi g to have to build a some sort a lead i can not get to the white wire with it hooked up. first test positive lead .08 Vdc Second test negative lead .07Vdc.
I will complete the third test he ask about the white wire as soon as I can. My question is there another fuse that may have something to do with the voltage on the green wire somewhere under the cab. I have not raised it. I have checked all fuses in the cab and they are all good.
Third test white wire to negative post 11.89VDC
Third test 11.89 Vdc
You didn't see my answer above. The green wire connected to the alternator goes nowhere. See Post #11. There is the main fues in the engine compartment. But if it was blown the engine would not even start.
I did see your I am just wondering what it would be there for. I was told that it was to enable the alternator to start charging. I was also told to put 12 volts to that spade and see if it would start charging but did not do that I did not want to cause more issue then I already have.
Whoever told you that was also not correct. it seems as though you have been getting some bad advice. To excite an alternator that does not want to come out to play and start charging battery + voltage should be applied to the R Terminal, not the P Terminal. It says there right on the illustration (note on the bottom RH corner)
Was the engine running, revved up and lights and heater fan on cause, #1 test should of given a number like 0.2-0.5 volts typically #2 test should of given a number like 0.3.0.5 volts if the lights are on and fan is blowing, your reading is about 1/10th of normal loss which tells me your meter is no good or something else could be wrong. You have to have some voltage loss in cables and connections, but too much means there will be problems for starting or charging. Maybe the electrical load is low compared to when starting is all I can think of. That being the case the test Arny said to do would verify if there is sufficient power to the white wire,, if it passes that something is wrong with the Alternator. Could be new and faulty, could tell you an hours worth of stories over the years with faulty parts. Trying to eliminate simple stuff first. If the cables are not compromised the alternator has to charge. Simon C
Niges explanation is 100% correct, anything you were told otherwise is wrong. It is the white wire that makes that alternator go as he has said. Simon C
Sorry I missed that one. Indicates there is something wrong with alternator as far as I can see. Simon C
Meter is good not an issue with it I have 3 or more Fluke meters I uses the daily. Yes motor rims above mid way lights and heater fan was on.
It's just funny how the alternator was working before the battery change and now not working and an another alternator giving me the same issue.
Maybe your new battery is defective, and wont accept a charge. got an old battery you can swap out.
Glad you have good Fluke meters. I have 2 Fluke 87-5 and a 1000 amp clamp also. You seem to have done exactly as asked, which leads me to believe that the problem is the alternator. If the excitation voltage is there it should charge. How far down does the battery drop while cranking the engine with the meter leads on the positive and negative posts. But if it was dropping low it would make the alternator charge like crazy in my experience once up and running. Pointing to a defective alternator to me. Just to let you know seen a D11R dozer drive into a shop and no start after. 3508 engine with dual starters. There is no way both died at same time. Sorry but yes they did. Sometimes things happen. You could try what Arny has sugggested with another battery but I am doubtful but will know eventually. Simon C
To completely eliminate green wire as the exciter, put 12v to it and see what happens, If info is accurate,( which it most likely is ) the green wire goes no where, and wont do any harm. Take alternator to a shop, and confirm its functionality. Out of ideas
There is no shop around here that can test have done tried going down that road.
i will try to get this test done this weekend. Thanks
well i guess I will be ordering another Alternator and go from there..
Try Arny’s test first then come back with your results before pulling the trigger on another alternator would be my suggestion.
Thanks ended up with another alternator and fixed the issue must have gotten a bad one the first time. Now have another issue if it not one thing it's another. My electric actuator will release only will not lock not sure where to go with this I was thinking relay but the chart on the relay panel inside is not correct because pull both relays the in and out and it still got power and was teying to release.
Frustrating to have to troubleshoot a problem twice. What actuator are you referring to?
So glad it turned out to be your alternator. As I said in Post #27 second line, the information that you gave back was pointing to the alternator. Just watched a video where 3 New ones were all junk from a remanufacturer, so this kind of stuff is happening. So it is your disconnect for buckets that is not working properly, will look at schematic later on here. Simon C
Attachment actuator
Glad the schematic that Nige supplied was correct about the white wire being the one that controled the alternators charging. Very hard to figure out anything without schematics. Simon C