Hi all! Been a lurker for a bit and have realized the amount of knowledge that people have on here. I have a cat 943 sn 19z00916 with a 3204. So far, the issues I have came across I have been able to fix but they've not been electrical until now (mostly). I bought this recently and changed out all the belts which made my alternator light go out for maybe 30 minutes or so of run time. Shortly thereafter, tightened the belts and light still existed...Not caring much about the light, I've used my machine and hoped I was keeping enough charge - I was wrong. Had to take the batteries out and charge them from the middle of a field. Thus, I took some measurements to help troubleshoot. With the old alternator (no info other than Ace Electric on the back housing) I was reading about 24.8vdc at the alternator at low idle and 25.1vdc full throttle. I also took a clamp on ammeter that should read DC amps and got 0 amp output. I then purchased a new alternator which I believe is a delco 20si 1 wire alternator rated for 28v 35a. Since I don't have any accessories really, I don't have anything connected to the R terminal. I just have a ground and the positive or battery wire. With the new alternator installed, I am now reading 27.2v at the alternator whether I am idle or full throttle and also between 6.15-6.58a between idle and full throttle. Not that I think it matters, but my regulator stab on the alternator reads 13.65v which jives with half the output voltage. With all that said, I still have a flickering alternator light on my operator panel with the new alternator installed, regardless of throttle position. My main question is whether it seems the new alternator is working or not, and if it is, do I probably just have some split wire somewhere in the harness going to the alternator indicator? This is my first time swapping out an alternator so I am not sure of 100% proper indications. Thanks in advance.
I think the original alternator indicator lamp received its signal from the r terminal. Off the top of my head. You might refer to the wiring diagram to verify that. But, ain’t nobody gots time for dat. If you went with a one wire, there is no provision for the indicator lamp. You will need a voltmeter in its place. Welcome to the HEF. Good to have you. What do you like to load with your track loader?
Thank you for a response! For what it's worth, the alternator I took off only had two wires, the battery wire and ground. I'm fairly confident the light went out after the belt was first changed but then hasn't been out since. I could be wrong but I could swear that's what I remember. Would you suspect - based on my information given above - that the new alternator is working properly? I also figure an inline ammeter would be worth it alongside a voltmeter like you mentioned. Thanks for the welcome! I recently purchased this so I have been using it for clearing and moving trees. The 4n1 bucket has been super nice considering I don't have an excavator yet.
The R terminal of the alternator is supposed to be connected to the Monitor Panel via wire 403-GN. A signal on that wire is what puts the charging light out. 403-GN is also connected to the hour meter so I assume that doesn't work either. The 6 SWG wire 109-OR goes initially from the alternator to the alternator circuit breaker. If you want the complete electrical schematic, just ask. It's not that flash quality-wise, but ought to suffice for what you need.
Thanks Nige. That’s what I was envisioning in my head. Guess you did have time for that.
I nominated you for the HEF outstanding contributor of 24. Did your award ever arrive?
Welcome to the Forums Dfs! Glad to have you. Nige does this machine have an air inlet pre-heater? The reason I ask is I had a similar problem with my 953C thinking it was batteries and then alternator only to find out the air inlet pre-heater was stuck in the "ON" position the entire time the switch was turned on draining the electrical system. Probably has nothing to do with it just thought I would share.
Thanks for the information Nige. I do have the service manual but will need to do some searching. If you have the electrical schematic readily available, that would be great! Also, my hour meter does work properly so I am not sure the discrepancy with the 403-GN wire. Also from what you are saying, sounds like the light going out with the belt swap may have been in my head if the original alternator I took off only had 2 wires? CM1995 - thank you for the additional info. I do not think I have an air inlet pre-heater. I don't have an enclosed cab. The only additional accessories I have that could be pulling power would be the fans on either side of the seat (very minimal electronics).
It's a heater for in the engine intake not the cab FWIW. I don't know the models that had them or didn't have them. Mine is a BBX series well after the 943 models.
CM1995 - gotcha. I don't think my machine has that but I will look into it.
Negative. TBH the electronic version of the electrical schematic appears to have been lifted from a number of sections of 50-year-old lithograph drawings, they didn't even line up the joints FFS...!! It's hard enough for me to follow even when I know what I'm looking for. If you have a fold-out paper version of the schematic in your service manual that would be far better IMHO, but if you still want it just say so.
I ended up searching my manual and did find the fold out with almost exactly what you showed. It is a slightly different schematic than what you showed but it still shows the R terminal of the alternator feeding into the panel. Maybe I was wrong with thinking the light went out since my old alternator didn't have 3 connections. We'll, Hopefully I can trace it out on my machine, I replace the lost wire, lose my flashing light when running, and have a good alternator. Thanks for your help. Last question: do the alternator indications i originally said lead you to believe the alternator was bad? I'm pretty sure it was due to the low output voltage but I could measure the amps. New one is in, just curious as to whether it needed to be done now that my missing R terminal was more than likely causing my blinking light...
Didn't think so but thought worth mentioning for others.
Sorry you're asking the wrong guy. I'm not one of the electrical gurus, but I'm sure one will be along shortly to answer your question.