Hello, I have a 2021 cat259d3. The battery is not charging. I have tested the battery and it tested good. I replaced the alternator with a new aftermarket one. I’m still getting the same 11.7v out of the new alternator. The old alternator was giving me 11.7v. I’ve tested the white wire with the key on not running and I’m getting 11.7v to it. I tested The green wire with the key on not running and I’m getting 0v to it. I’m just confused at this point. Any thoughts? Serial number: cw903533 Codes: E875-2 167-4
If you have not seen this. HeavyEquipmentForums May give you some general ideas.
I sent an electrical schematic to your message inbox.
So now I’m still confused. The wiring diagram is saying that the green wire goes to nothing and “conn 33” Is it a 0v wire?
In the mentioned thread it is for an optional tach. Only an issue if the aftermarket alternator is wrong internally. The white wire is connected to r in the schematic in the other thread.
Extract from the electrical schematic. Wire 403-EJ112 would only be used if the machine was equipped with a tachometer - which it isn't. It's simply part of the standard engine wiring harness. The 123-EJ111 WHite wire is Batt+ coming from the key switch.
So it is not unusual for the color of the wire in the schematic to differ from the I’d label such as 123-EJ111 WH-18 is green in the above schematic?
Sorry you have your lines crossed. From the above snip - 403-EJ112 GN (upper LH) - optional tachometer signal, is a Green wire 123-EJ111 WH (lower LH) - Batt+ from key switch, is a White wire
Im not making myself clear, my fault. This may help. Green or greenish to my eyes. Thank you.
You are falling into the same trap as many people. The colour a wire is drawn on a Cat electrical schematic indicates the wire's function and bears no relation whatsoever to the colour of the wire on the machine. The table below may clear things up. The 123-EJ111 wire is actually WHITE in colour but is drawn in BLUE on the schematic because it has battery voltage in it when the key switch is ON.
Thank you Mister!
I have figured out the problem. I took An alligator clip and clipped it onto the alternators (L) plug. Then put a spade end on the other side of my alligator clip wire, plugged it into the 123-EJ111 white wire/EJ-C8 plug. Turned on the machine and it started charging. I was able to pop the wire out of the EJ-C8 plug and put it in the bottom of the EJ-C8 plug so it’s a factory look/fit. I’m thinking maybe the alternator is wired wrong? Seems weird but it’s working. While the machine is sitting idle it is charging a bit high 15.1v When I'm operating the machine it’s charging 14.7v What are your thoughts about this? Thank you!!
I "assume" that the old alternator was functional at some point and was wired "correctly". How does the wiring of the old alternator compare to the new aftermarket one?
I wonder if the replacement alternator required externally exciting to get it to work the first time.? Have you tried removing the jumper wire since.? If not do that and report back.
Yes I have removed the jumper wire. I popped The 123-EJ111 wire pin out of the EJ-C8 plug and moved it to the bottom side of the EJ-C8 plug. With it in the bottom side of the plug it is making connection with the (L) on the alternator and leaving the (R) blank.
Yes it did work at one time. I’m not sure how it was wired. I took It apart but I kinda had to destroy it to get it apart
Can you try moving the 123-EJ111 wire back to its original position in Pin 1 of the EJ-C8 connector and see what happens.? It may be that all that was required was to temporarily supply batt+ to Terminal L of the alternator to kickstart the excitation.
I will Try that this afternoon. I will Report back! Thanks!
Have seen a few alternators in the past that needed a momentary spark of power to get the magnetism going again. Seems from my experience that it happens after a machine has been shut off for a long time or alternator has been a long time on a shelf. I could be wrong. Simon C
I did the alligator clip on the (R) terminal and the spade onto the 123-EJ111 wire/EJ-C8 plug and turned on the machine. The alternator would not charge the battery. I put The plug back in the alternator (pin 2 of plug EJ-C8… plugged into alternator terminal L) It’s still charging at 15.1v What are your thoughts about this? Thanks!
Your batteries state of charge can determine how much the alternator puts out. If from the alternator B+ Terminal to battery positive has any dirty or corroded connection, the alternator will sense lower voltage and put out more. Thats what I seem to recall. On start up it is common to have a little higher charge till the battery charge becomes stable. You could test from the Battery + Terminal of your alternator to the Positive of your Battery with your meter on DC Volts. Red test lead at Alternator Battery +, and Black test lead on the Battery Positive with the engine running, revved up and lights and fan on. If meter records more than 0.5 volts you know that something is wrong in a connection in between. Good to do this test before looking for another Alternator. A charge rate of 15.1 volts will eventually boil a battery. Simon C
Forgot that since the Alternator Positive Post goes direct to the Battery Positive Post through the Large Red cable the voltage drop should be more like less than 0.2 volts if all is clean and nothing burn't out internally. Check it out and let us know what it tells. Simon C
Ok thank you! I will look into this tonight!
This is not rocket science. Back to basics. With the machine off, do you have 12 VDC (battery voltage) at the B+ terminal on the alternator? You should. If you don't, you have a break in that wire that goes to the battery. Next check to see if you have power to the (R) terminal while running or at least with the key on. With the key on, you should be sending 12 VDC to the (R) terminal. That signals the alternator to turn on. If you do not have 12VDC to the (R) terminal, the alternator will spin but put out nothing. Also, I think you said earlier that your battery voltage was 11.7? The battery is low. You should charge it back up before proceeding.