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I THOUGHT I "fixed" my battery charging problem

1220 Views 25 Replies 8 Participants Last post by  jbarnett250, 
J
I bought my 2010 Murano cheap because the previous owner was tired of it stranding her on the road randomly due to the battery going dead. She was going to donate the car just to get rid of it so I bought it for $500 thinking I could probably fix the charging problem and if not I wasn't out much. When I got the car the radiator was leaking all over the alternator so I replaced that and the problem hadn't happened again for a couple months so I thought maybe the radiator replacement had resolved the problem. But last week the car stranded me on the road. I had watched enough videos about the smart charging control and the various problems that can be associated with that system so I knew the general direction to look. I started by looking at the troubleshooting tree in the FSM. The 2nd step of that process is to disable the smart charging and evaluate the various voltages. One method to disable the variable voltage regulation is using the consult II device and the other is to unplug the battery current sensor. No matter what I did I couldn't unplug that current sensor. It's in an awkward location to grab and it's connected to a harness that doesn't give you much room to manipulate it. Even using pliers to try and press the connector latch and pull on the connector, I couldn't get it to come loose. So my troubleshooting ended right there. I had seen some videos about how to disconnect the control signal for the variable voltage regulation at the IPDM which will disable the variable voltage control. This one has good instructions on how to pull the wire from the IPDM connector:


Once I pulled this wire, the voltage regulation defaults back to standard alternator behavior where the output is fixed at about 14.2-14.4V. I have a feeling my problem is at the alternator connector but access to that connector is so tight that I don't want to try and replace that connector unless I have to. The only special tool you need to pull the wire from the IPDM connector is a small pick or something to open the tiny terminal latch inside the connector. It only took me about an hour of research in the FSM to be sure which wire to pull, open the IPDM and remove the wire and test. If anybody is having problems with intermittent battery charging this is an option if your alternator is good. Like if it charges normally most of the time like full voltage at startup and it controls the variable voltage output shortly after startup to about 13.2-13.6V. If you see this behavior you know your alternator and the control system works SOMETIMES. The problem is it will intermittently crap out and discharge the battery on you while you're driving. It's relatively simple to disable the variable voltage control to try and see if this resolves your problem. If you remove the wire from the connector rather than cut it, it's easy to put it back. Something free to try to prevent you from changing your alternator 3 times and killing 3 batteries before giving up and selling the car.

It's only a been a week since I did this so we'll see if this holds up long term. But I definitely like seeing the alternator output at 14.2V all the time now like every other car I've ever owned.
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I need coffee
I suspect the source of the problem may be some internal fault in the voltage regulator that's causing it to intermittently shut down. Whether VVCS is enabled or disabled, the voltage regulator controls the alternator's output either by carrying out the ECM's command or by using it's own defined parameters if VVCS is disabled. However, the inputs for determining alternator output are different in each case. The input the ECM uses for the VVCS system is based on current draw from the battery via the signal it receives from the battery current sensor. The alternator's input when VVCS is disabled would be the voltage detected at the alternator S terminal. I think you've basically determined that regardless of the input, the alternator is intermittently not charging. It could be some problem with the B terminal wire that goes directly to the battery so definitely try to rule that out. I would suggest a voltage drop test on the positive side of the charging system if you can get to the B terminal (...connect DVOM leads to alternator B terminal and battery + terminal). Voltage drop should be no more than a couple of tenths. Jiggle the harness and see if the voltage jumps.
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I need coffee said:
I suspect the source of the problem may be some internal fault in the voltage regulator that's causing it to intermittently shut down. Whether VVCS is enabled or disabled, the voltage regulator controls the alternator's output either by carrying out the ECM's command or by using it's own defined parameters if VVCS is disabled. However, the inputs for determining alternator output are different in each case. The input the ECM uses for the VVCS system is based on current draw from the battery via the signal it receives from the battery current sensor. The alternator's input when VVCS is disabled would be the voltage detected at the alternator S terminal. I think you've basically determined that regardless of the input, the alternator is intermittently not charging. It could be some problem with the B terminal wire that goes directly to the battery so definitely try to rule that out. I would suggest a voltage
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C
On my 2011 Murano, the B terminal was broken off inside the alternator
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J
4
Good job getting it out and confirming the actual cause of your failure. I'm still fighting with my intermittent problem and putting off removing the alternator from the car because it looks like such a crappy job and I'm still not 100% sure it's the alternator and not the wire harness. My B terminal looks good as far as I can see it which is not much while on the car. Doesn't look melted. Nut and stud and ring terminal look totally normal so I don't suspect I have a broken B terminal inside that would cause heating like yours.

But I pulled my alternator plug off this weekend to have a look and it also looks really good. It was brittle from age and heat and the latch broke off trying to remove it. But it looks pretty good inside. I tried to run the car without it plugged in and the alternator doesn't make any output like that. The three signals on that connector are the PWM from the IPDM which I've already disconnected at the IPDM. The signal to turn on the charging light on the combo meter which doesn't come on even when I'm not charging and I don't really care about anyway since I have an indicator in the car that tells me if I'm charging or not. The last connection is the S terminal which sounds like a sense terminal rather than a control terminal like for the field or something. But without knowing exactly how this voltage regulator works, it still seems possible to me that losing the S terminal connection to battery/fusible link could cause my alternator to have no output (based on me disconnecting the plug and getting the no output condition). So I fiddled with the connector and shot some contact cleaner into it and plugged it back in and everything is fine at the moment but who knows for how long. If it acts up again I'm going to splice a replacement plug onto my wire harness before committing to pulling the alternator out.

Did you post any pics of the b terminal failure in your other post? Would be good to see how that fails.

pic 4049 is my oem alternator plug showing latch that broke off during removal. The flex conduit stuff was brittle and just fell apart when I handled it. But the wires seem ok. Not melted and not really even stiff so I don't suspect a problem with the wires themselves.

pic 4051 is looking into the face of the oem connector. It looks ok to me too. Nothing melted or hogged out like it wouldn't make proper connection.

pic 4052 is the connector on the alternator and it looks ok to me too.

pic 4053 is the replacement plug i bought off amazon. I read some other thread on here where somebody replaced that plug to fix their problem so I bought for about $10 anticipating needing to change it. I think I'm going to bypass my harness and fuse and run a separate wire to the S terminal on my replacement connector before cutting out the oem plug. If bypassing the harness and fuse box with the replacement plug doesn't fix the problem, it has to be somewhere in the alternator.

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The B terminal stud turned freely when I tried to take off the nut that holds the alternator charging wire to the post on the alternator. All the plastic had broken up and the internal wire that connects to the post on the alternator had completely broken or melted.

It wasn’t actually the worst job in the world. Take off the oil cooling lines and move that assembly out of the way and move the ac lines that sit on the frame out of the way.

I also removed the upper radiator hose that runs parallel to the radiator.

I removed the four compressor mounting bolts and dropped it down as low as it would go.

I took off the upper and lower idler pulleys.

When you remove the nut that attaches to the
bolt on the lower left of the alternator, use a deep socket as the end of the bolt sticks out far enough that a shallow socket won’t fully seat.

The 12 mm upper alternator bolt near the B bolt is hard to see but you can view it from below and it’s not too hard to rig up some extensions and a universal joint to get it. Once I took that out, I removed the lower bolt and wiggled it right out. Went back in pretty easy. Put the lower bolt in first,rotated it so I could get at the harness connector and nut on the B bolt. Then I got it aligned to the upper hole as best so could see, then reached around from the front with the bolt and wiggled till it went in.
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J
Looks like I have to swap the alternator after all. Even bypassing the harness and using a new alternator plug the intermittent no charge is still present. It's getting less intermittent and more consistent the last couple of days. Time to get an alternator. One thing I haven't done since buying the car is replace idler pulleys and new belt and tensioner. The alternator troubleshooting said that a loose belt would cause the charging light to light at idle which I don't have so I wasn't really going down that route. But I should probably do those parts anyway just because they're probably old and there's a slight squeak from something over there on cold starts for a couple minutes. I tried to figure out which component is making the noise but can't isolate it. I might order all those parts along with the alternator and swap them on first just to be sure it's not a loose belt before I finally give up and replace the alternator.... one of the recent times the no charge condition popped up was immediately when I engaged the AC compressor. Not sure if this could have been because of change in electrical load or change in load/tension on the belt but just to be 100% sure I don't change an alternator that isn't bad, I'm going to put on a new belt and tensioner just because. Then alternator.
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