The other day I drove the car for a good 40 minutes, then parked and listened to the radio for about 15 min with the key in the ACC mode. When I went to start, all I was getting was a click. I ended up getting my car jumped. So I went home and for kicks I started to check voltage at idle with the following accessories turned which is what I usually use in the morning: headlights, defrost, blower motor with A/C pump turned on. When all these are turned on my voltage drops to 12. 40 and keeps dropping slightly and very slowly but pretty much stays around that voltage. If I shut off one of those accessories, Voltage goes back up to around 14.2. I know that's a lot of accessories to run at idle, however, the alternator should be able to keep battery over 12.6 volts. If I do rev the back a bit past idle like let's say around 1000 rpm's the voltage is fine around 14 so not sure if to condemn the alternator at this point. A difference of about 150 rpm's puts it in charging state although technically at idle there should be enough juice to charge the battery. Does anyone has this voltage behavior with their voltage? Thinking the regulator is shot in my alternator.

 

I have an 03 SE, and you've just described exactly the same symptoms that mine has. My battery hasn't died on me yet, though. I'm also curious to know what it could be. I was told maybe the alternator is on its way out, and I should have it replaced. No warning lights on the dash, and the engine starts just fine.

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I have a 2k and the behavior sounds like what mine does (minus the failing to start).

I've noticed recently that even my lights dim somewhat with all that on below about 1k rpms.

My guess has been battery since I abuse mine. But I have not had a no start problem . . . so maybe it is more likely alternator.

Are you testing at the alternator or at the battery?

 

Your alternator is doing just fine. I have a 2000 with a known good battery and the voltage readings I get on my car are pretty identical. Alternators do not produce maximum output at idle, so this is to be expected.

If you are concerned about your battery, check the voltage on it after you park it for the night and then in the morning. The voltage should be pretty much identical to when you parked it. If the voltage is down more than a tenth, have a real battery test done on it.

 

^^ agreed When performing the voltage with the accessories on have some raise the rpm and see what happens

 

I can see a lower (12-13 Volt) reading at idle with full loads, but that Voltage should never drop much during the test. If it is the battery isn't holding a charge well, needs water (if it's serviceable type), or the alternator or wire connections aren't up to snuff.

I've never had a car that didn't hold 12.8+ Volts with every load on, stereo on, etc. except for when my alternator was on it's way out, or not working. I have had 1 battery that did the same thing you mentioned that needed water, after that it lasted a few more weeks before it needed replacing. It Just wouldn't accept/hold a charge fast enough