I'm with ljdiscovery. When the oem alternator finally went on my 07 a couple of months ago, I wrestled with either a rebuilt/auto parts store unit, a wrecking yard pull, OEM, or getting the rebuild kit and rebuilding my factory alternator myself. I chose the last option after doing a fair amount of reading. The rebuilt units are a total toss of the dice. I tend to think, based on your descriptions, that your rebuilt unit is bad.

 

Thanks for the thoughts on this guys. I've been traveling for work and haven't been able to reply. I recently replaced both the battery and then the alternator. I realize this sounds like an alternator problem, but I'm gun-shy of going down that road again. Although I can do a great deal of work on it myself, I wasn't keen on the idea of laying underneath it in my driveway. So, $300 later I had a local shop (that I trust) make the swap from the old original alternator to a newer after-market one. However, I suspect that whatever this issue is, was there before I replaced the alternator. Only because I kept having an issue of the hesitation when I started it from time to time for a month or two before it failed completely. So, I can't seem to eliminate some other sort of issue with it.
I'm willing to spend the money, time and effort to replace the alternator again, I sincerely believe looking back at it's performance prior to the alternator change, that the issue was already there before I replaced both the battery and the alternator.

As an update - Before I left for my business trip, I went for a drive one evening. For the first 20 minutes the voltage hovered around 13.2 to 13.8. I was starting to think the problem had resolved itself. But then it would drop to 12.5 occasionally then kick back up around 13.2. I was about 30-40 minutes into my drive and it dropped 12.4 then 12.3 and continued to drop. Knowing how close I was to home, I just let it go. Got to my house and it had dropped down to 11.7. I left the engine running and popped the hood. Put my voltmeter around where I could see it. I shook and wiggled the F20 (5 amp) fuse to see if there was any change and nothing. Then I went ahead and pulled it out completely. The voltage went up from 11.7 to 12.3, and I could hear the alternator kick in and whine. But, it only stayed that way for about a minute and the voltage started to drop again. I did notice that the battery light on the dash came on, so I'm certain there is nothing wrong with that fuse or holder, otherwise I'd notice the battery light on the dash. I plugged the fuse back in and it made no difference, the voltage continued to drop. I banged on and wiggled just about every place I could think of, but no change. Finally as the voltage dropped to 11.6, I shut it off. It was slow to crank, but it started up again and I had the familiar array of warning lights on the dash. However, the voltage shot right back up to 13.5.

My next adventure (as soon as I have time), I'm going to tear out the passenger kick panel and look for this connector that people on here have talked about getting contaminated by the sun roof drain tube. This DID indeed all start a couple of weeks after a large rain storm (a rare event in Arizona). We shall see how this next step goes. I'm still open to suggestions. Thanks for everything thus far.

 

A suggestion is that when you turn the starter motor it puts spikes into the ECU so stopping it from starting especially if battery is low. The answer is to run an earth cable from a bolt on the engine to the negative earth point on the body. This may fix your problem.

 

Globetrotter, Thank you for this suggestion. I've measured the resistance from the body to the engine and have found no difference. I did remove the right front tire and checked, and cleaned the cable that goes from the body to the engine. So, I don't think this is at issue at the present time. Thank you!

 

Today I finally bit the bullet and replaced the alternator. Even though I had previously had it replace, I decided perhaps I got a bad one.

I'm sadden to report it made no difference! I start it up and it charges just fine for roughly 10 minutes. Then all of a sudden the voltage just starts dropping. It never charges again after that. Voltage will continue to drop until I finally turn it off when it reaches 11.7 volts (at 11.6, it won't even try to crank). Once I restart it, it will jump right back above 13 volts and I'm good again for about 10 minutes.

I'm still open to suggestions cause I'm pretty much all out of ideas. I'm starting to get suspicious of the ECM.

Thanks for the help thus far, I am open to ideas.

 

Avery interesting problem. The alternator controls the charge to the battery so this gives the impression that the battery is charged up (but it is not). Now that you have replaced the alternator have you another battery you could swap in to test and see if you get the same results as it may be possible that a cell shorts/shorting out

 

The alternator does not control charging, its driving my the ECM. Hence the 3 pin connector. I wonder if this connector is damaged in some way, they are known to be rather fragile which is why I bought a spare for when I charge the alternator.

GENERATOR
The Generator has a multifunction voltage regulator for use in a 14V charging system with 6÷12 zener diode bridge rectifiers.
The ECM monitors the load on the electrical system via PWM signal and adjusts the generator output to match the required load. The ECM also monitors the battery temperature to determine the generator regulator set point. This characteristic is necessary to protect the battery; at low temperatures battery charge acceptance is very poor so the voltage needs to be high to maximise any rechargeability, but at high temperatures the charge voltage must be restricted to prevent excessive gassing of the battery with consequent water loss.
The Generator has a smart charge capability that will reduce the electrical load on the Generator reducing torque requirements, this is implemented to utilise the engine torque for other purposes. This is achieved by monitoring three signals to the ECM:
Generator sense (A sense), measures the battery voltage at the Central Junction Box(CJB).
Generator communication (Alt Com) communicates desired Generator voltage set point from ECM to Generator. Generator monitor (Alt Mon) communicates the extent of Generator current draw to ECM. This signal also transmits faults to the ECM which will then sends a message to the instrument pack on the CAN bus to illuminate the charge warning lamp. For additional information, refer to Generator (414-02B Generator and Regulator - 4.4L)

 

Attached a PDF on the alternator/generator. That PDF references the charging system operation starting on page 11 of the other PDF attached.

 

I really appreciate the comments. Here's what I know about those suggestions - I replaced the battery when I first started having issues. A bad cell in a battery will cause a slow constant drain on the battery. This current battery will recover on it's own. In other words, if the battery voltage is at say 11.7 when I turn off the vehicle, if I let it sit overnight, it will recover up beyond 12 volts. If it were a bad battery or cell, it would never recover on it's own. Basically once the alternator quits, after about 10 minutes, my LR is running solely on the battery at that point in time. So, if anything it's the hero in all of this.

As far as the 3 pin connector going into the alternator, I checked it very carefully when I had it apart yesterday. It's still in good shape, pretty much bright and shiny connectors. I'm really thinking one of two things at this point. Either it's temperature related, or I've blown the ECM somehow. Truly charging is controlled by the ECM using pulse width modulation. I guess I could snake a wire down in there and hook up an O-scope to watch what it does while I'm driving. I'm just baffled because no matter what, it works great for about 10 minutes then voltage starts to drop. If I restart, I'm good for another 10 minutes. It makes no difference sitting still or driving. Yesterday my son timed it with a stopwatch and sure enough just idling in my driveway, at 10 minutes on the nose voltage started dropping.

Really appreciate the help guys, I am completely baffled!!!

 

A very interesting read of the pdf's. It seems that the ATCM manages the load required from the battery and informs the ECM if the engine needs to speed up so increasing alternator output. Could the reverse happen? shutting the alternator down. The ATCM is the module that has the a/c dials on it so may be needs a look at as the tables show some timing - ie 10 mins when cold and what is required from battery (load).