The thing was the fan's been dead since we got it, it's gone at least 20K miles and probably much longer that way.

And then something decides to short out. It just hadn't occurred to me.

All the alternator monkey-motion was probably completely unnecessary, but it's my wife's daily driver and I wanted to get the thing fixed ASAP. Ah well, act in haste repent in leisure, or lack thereof. Now it needs brake pads...

One other point of note - when I connected the meter to the yellow-zinc plated jump-start post under the hood, I got 0.4V less indicated than when I put the clip on the phosphated or cad-plated or whatever ring terminal on the cable that it bolts to.

Make sure if you're going to clamp to those jump-start posts that your clamp is sharp enough to bite into the metal.

I was wrong, it WASN'T the fan. But I now know EXACTLY what it was, and it's fixed and isn't coming back.

Sometimes you find the answer, but it just doesn't occur to you...you go right on past it. Remember earlier I said the batt + post on the firewall was 13.2-13.3V but the the ring-stud on the cable behind it was 14+?

The problem came back today. Went to check the usual suspects with the meter...and when I inadvertently touched the + post with the plastic test-probe sheathing it started to melt and smoke.

The post was hot, very hot. The whole cable was hot.

This is the first X5 I've ever wrenched on, and I didn't realize that stud base is actually a pass-through to the power cable for the rest of the car. But that thing wouldn't get hot unless it was passing current. So I opened the plenum and voila - there's the other side of the battery cable. And after it cooled down...sure enough, the ring terminal was loose in between stud and base. Once removed, there was clear evidence of arcing in there, and the plastic around the base of the stud was a little deformed though still intact.

It would appear that when I was poking and prodding it with the meter last week I jostled it around enough to make contact for a while, at the point at which I'd unplugged the fan, but eventually it went bad again.

A little quality time with a sanding drum and wire wheel in the Dremel, a little silicone grease, and it's all back together and charging nicely. Dropped the snap-on cover for the rear side of the cable down inside the plenum somewhere, wonder if I'll ever get it out of there...

Hey, at least you found it. Good on ya. :)

Post a "Fixed" in the title now so others can find it should they have this little gremlin pop up.

Yeah, the fan thing was a head-scratcher but the current to the battery DID go up, and stay up for at least a day, when I unplugged the fan.

I'd guess that in checking the voltage at the stud I'd moved the terminal around a little with the clip on the test probe, just enough to provide a temporary improvement in the connection. Heisenberg strikes again.

I don't recall the stud being so hot when I looked at it previously, though I probably didn't touch it with anything but the clip of the probe while the engine was running. The stud itself was tight on the threads - as it turns out it was kinda seized in place, and took a lot of muscle to get loose, even though it wasn't particularly tight against the ring terminal.