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One of those dreaded alternator failure, replacement, still something wrong issue solved!

411 Views 13 Replies 3 Participants Last post by  2ndGenMaintainer
Hi Family!

Recently had the alternator brake and battery light issue. In this case, I had a bad voltage regulator harness found while removing alternator. Soldered and shrunk a new harness on improperly. Had same issue as before new alternator.

Key issue: charging system tester reading "charging high". Limp mode after driving a few minutes, but brake and battery light are off.

Solved in this particular case by correctly wiring new alternator voltage regulator harness.

For some reason I can't get into the nicoclub manual to verify wire color coordination. However, this link is to a video where this very kind gentlemen layed it out very easily.

The harness being melted before the alternator was replaced, was most likely causing the limp mode symptom. Still yet, after I replaced the alternator, I mis-wired the harness and it still had the same symptoms. The old alternator may have very well been fine in this case with a bad regulator most likely. Unfortunately, I won't know the answer to that question.

107k first replacement of alternator!!

100% honesty : failed to securely tighten battery post terminals. My negative bolt rusted/rotted and I thought I was tightening it while it was actually just spinning. I didn't catch it till now. My fault I think. Probably caused heat at the alternator voltage regulator harness connections. I did notice some corrosion on the battery terminals at time of service lol.
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I think the melted alternator plug/harness thing is kinda common (seen a few videos of people repairing these) so I'm not sure your loose cable clamp was necessarily the root cause. I suspect I had a plug/harness problem in my 2nd gen too that intermittently caused a no-charging condition until I disabled the vvcs function that is controlled and sensed at that plug. But it's so tight to work in there I'm putting it off replacing the plug. I bought the replacement plug but am just dreading doing it. Did you drain the coolant and remove the top radiator hose and fans to do that plug splice job? And do it from the top or the side? Take any photos of your job? Would make a good DIY.

The FSM recommends to disable the vvsc as the first step in any no-charge troubleshooting by disconnecting the battery current sensor. This will tell you if your regulator is still good or not by disabling the external controls that could make it appear like your alternator isn't working. I couldn't get mine unplugged but that's how the FSM recommends to start troubleshooting to avoid misdiagnosing the alternator as bad. That looks like alot of tight and tricky work to DIY the alternator swap only to have the same problem after.....

You might try another browser if you can't get the nicoclub site to work. I can't get the manuals to work in Chrome but Edge(!?) works for me. Might just be some browser settings I've made in Chrome and never made in Edge because I never use it. Those manuals are key to figuring so much stuff out.
Ah I see, ill try using a different browser thanks!

Thanks for the info about the vvc too!

I did the soldering and shrinking from the top, but this was before I attached the positive post to the alternator for slack purposes. Then I had to remove this regulator harness from the alternator after I realized I miswired it. So I took a wire hanger and made a long tool to depress the harness clip while I tugged up on the wires in order to pull the harness out from secured in the alternator. I then squeezed my hands in once again and just cut, soldered and shrunk tube on the wires again but making sure the colors were correct this time. Then I used a long extension to push the harness back into the alternator. It wasn't too bad, just a little tight getting down in there to twist the wires together before soldering.

While soldering, i unrolled a long lead of solder so that I could work it back and forth on the solder gun from up top. Held onto the soldergun/wand with my fingertips down and to the wire where I fed the solder onto the tip with it touching the bare parts of the joint and just worked the tip back and forth on the joint. Hope that makes sense lol.
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Good day!

Good find! Looks like you could try replacing that harness and see if it fixes all of your issues. Keep in mind that at least for the muranos, the alternator can be hit and miss lately on whether or not you get a good one and depending on the brand/cost. I say that because many of diyer here has reported bad out-of-the-box alternators or even ones that don't last very long at all. It was not fun changing the alternator and I dont want to have to do it again. BTW, I chose to drop the ac compressor to get the alternator changed out added a bit more time but alleviated the need to drain coolant and remove radiator/condensor. I got lucky with the Duralast gold so far, fingers crossed, knock on wood! Lol. Good luck and let us know how it works out!.
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It was a whole hell of a lot of work.. I'll never buy a transverse v6 ever again.. sadly it seems all manufacturers except for Toyota are only concerned with ease of assembly, but not maintenance..

Here's what I found for 2 wire murano alternator wiring diagram. Not sure if its for your qr25de. It might be the correct diagram if there is a yellow/b-stripe and a brown wire there. If so, it looks like the brown wire is the sensing wire with a meter. I dont see any IPDM in this particular page.

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2ndGen, strange timing but I saw a Nissan Maxima dies while driving video today that sounds even more like your original failing alternator situation. Don't know if you've ever seen Eric O. on South Main Auto channel on youtube but he does a bunch of good diagnosis videos and this one happens to be on our exact charging system. In this video he gets a Maixma that goes into some kind of limp mode due to high charging voltage rather than the battery dying from low voltage. This one would flash the battery light sometimes. He ends up replacing the alternator and not the harness even though the Nissan dealership quoted $2000 to replace the harness. They must have been thinking it needed that plug/harness replaced too.

He cleaned up the battery connections in this one too because they looked crappy so maybe the loose battery connections had something to do with the original cause of the alternator failure after all.

Check out this video and tell me that doesn't sound like your car's behavior..... there's a part 2 where he completes the repair.
I love south main auto, my favorite!

I used to watch a lot of rainman Ray too but I think I just outgrew his content. Ray's a nice guy and a great mechanic but for some time now I've wished that his content would evolve a bit past the basics. Wish him well, but Eric O and Mrs. O are my all time favorite. Been a while since I've seen him do a two part on a diag. His methodology for troubleshooting is superb. A lot to learn from him for sure. He keeps it interesting.

Diagnose Dan is another superb diagnostician on YT. You may have seen him shouting out SMA a couple times.

It definitely sounds like the same exact issue I was having. Too bad I didn't find it before I bought a new alternator. Knowing my luck though, if I had, then I'd probably still need a new alternator lol!🤑🤑
Yeah thats kind of where it seems we all end up even with slightly different symptoms. It seems that it may just be a regulator problem and possibly not the entire alternator.

You may have air still in the system somewhere, but I assume you already ruled that out. Sometimes it can be the impeller inside the water pump failing. Or an intermittent power issue with the water pump. The temperature sensor is most likely intact. Worst case obviously possible head gasket, but I wouldn't hang my hat on that.
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