At least it's a car - 2011 Caravan battery light

Need some tribal knowledge as somehow my scanner is not working. After a few minutes of driving the battery light shows up - alternator or charging system somehow (terminals, ground, etc), right?

Missing anything?

Check them all, but start with a voltage check at the battery with the car off and with it running.

Car off - voltage less than 12 = battery

Car on - voltage less than 14 = alternator

Put a voltmeter on the battery, should be something like 14 volts when its running if you have a good alternator. Note that if the alternator is going the battery(car off) will read low, and a bad battery will take an alternator with it sometimes.

The voltage could be lower than 14 if the battery is fully charged. Check it at idle, no loads. Should be at least 12 if the engine was started more than 30 seconds ago. Then turn EVERYTHING on, (lights, HVAC fan(s), defrost, seat heaters, wipers, and raise the engine to about 2K or so. See if the voltage jumps up to 14-15.5 or so.

I did this.

(my voltmeter sucks, but works, real numbers are not available)

Engine off, voltage across terminals = X

Engine on, idle, nothing else on, voltage across terminals = X

Disconnect positive lead = stall

Alternator, right? Is there a fusible link or other such silliness on one of these?

Hmmm, a recent Caravan? Is this just your first electrical issue? In the owner's manual it recommends increasing the revs, and seeing if the light goes off, so it sounds like it's basically a low-voltage warning.

The original battery in ours (2010) died a rapid death at 20,000 miles. (A cell died internally somehow, wouldn't even jump)

It is very bad to unhook the battery of a modern car with it running, dont do that again. If you aren't seeing a voltage jump at startup, the alternator died or isnt being energized for some reason. Newer cars can control the output to improve economy, battery life, passing power, etc. I'd pull the alternator and have it tested.

Revving it up with our without headlights on caused no differences in the voltage output.

Kenny_McCormic wrote: Newer cars can control the output to improve economy, battery life, passing power, etc. I'd pull the alternator and have it tested.

Ahh, so a switch of some sort could not be telling the alternator to alternate. Interesting. We're still under a powertrain warranty, although I doubt either an alternator or a sensor/control/computer widget would be covered.

Pulling the alternator doesn't appear trivial, so I'm not super looking forward to that.

Alternator gets turned on via the PCM and has its output varied from information obtained from the battery temperature sensor.

Basically, you need a fairly recent scanner that can read the datastream and see what everything says and go from there.

You could try dead heading it(car off, key out, unhook battery, stand on brake pedal and try to start, remove key, reconnect batt), though this will prove to be a setback (no data logs) should it be a recurring computer related issue.

Dealer says if it's the PCM (voltage regulator) it's covered under warranty. If it's the alternator, it's $100 for the diagnostic and I can go from there, so I just dropped it off and rode the bike home. We'll see what they say. With my workload/kidload, it's well worth $100 to pay them rather than pull the alternator myself and bring it to O Reilly's to see.

Thanks guys.

OK guys, I did something I am ashamed of. I let someone else work on my E36 M3 even though it wasn't under warranty.

They wanted to sell me an alternator via the parts department for $360 and I paid $100 for the diagnosis to point at the alternator rather than something else. Considering where it is located on the engine, I was glad to pay the $100 to avoid pulling it and going to the store with it, especially since the parts stores, including RockAuto, do not carry it yet at all. So I would have paid $480 after tax or so. They offered to change it for me for $498. OK, done. Have at it guys. Apparently the parts department sells it to the service department for $100 cheaper than I can buy it for. I can live with this.

I drove there with the mountain bike in the back, rode it the 2.5 miles (well, more like 5. I got sort of lost. I found a neato trail that looked like it headed the right way. But... it didn't.) and dropped it off, and then picked it up via bike ride when they were done. Considering I spent $18 (or $58 if they quoted me without the core at the parts department) I am totally OK with this, Even if I feel like a dirty whore now.

At least I got a great bike ride out of the deal.