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I have a 2002 Civic, 110,500 miles. Believe it or not, it still has the original battery in it. (It hasn't really been giving me problems, though I also haven't explicitly tested it either.) Also maybe-but-probably-not relevant is that I haven't gotten the 110,000 scheduled spark plug change yet. I have an aftermarket stereo head unit, but I don't think it's anything special. (I wanted a line-in and CD player, not to have some super-loud system.)

I personally only know a little bit about cars and have next to no experience doing maintenance, but I'm also willing to try stuff. (This generic thread, for instance, seems out of my league, at least without explanations of how to determine each of the choices.)

What happened this morning:

I stopped the car, I think left it on accessories for a little under 10 minutes, and when I went to start it again, nothing. There was a very weak clicking noise, but that's all; it didn't sound like it was really trying to start. The sound is familiar from the couple times I've run out my battery. I procured one of those self-contained jump-starter devices, tried again, and it started fine.

Following this, when driving along, when the engine was getting gas there was sometimes a sort of whrring, whining noise, changing pitch with engine output/rpms. Particularly prevalent at lower speeds (~20-30mph), but I don't know if it just wasn't there at higher speeds or if it was just drowned out by engine & road noise. After driving around for a while, I think this seemed to go away.

I also had an "interesting" experience where I turned on the front defogger. In my car this turns on the A/C too. (Unrelated question: this is obnoxious. Is it possible to make it not do that?) When I did this, my headlights dimmed or went out, my dashboard lights dimmed, and I forget if my stereo hiccuped. I felt like the car almost wanted to stop. Everthing went back fine when I turned the A/C back off.

I got home, parked, got out of the car, went to lock the doors, and... nothing. I think my automatic door locks wouldn't even work.

What happens now:

When I try to start it, I just get that clicking sound again. Furthermore, I got someone to give me a jump start, and even with that set up, my car won't start -- just more clicking.

I measured the voltage across my battery terminals at 9.8V, which of course means it won't start on its own. However, it's also seems like that could have happened if the battery was fine during the first jump start, somehow the car started, but the alternator wasn't going and the car was running off of my battery when I thought I was charging it.


Questions:

So, does this sound like it's the alternator? Is there anything I can do to try to confirm or refute this? Any other things to check? Could it, in fact, be the battery after all?

If it is the alternator, how easy is it to replace? I found this and it doesn't look too bad. How likely would I be to royally screw things up and cause more damage?

 
Rep Power: 244

You can get the alternator tested at a parts store like Pep boys. If the battery is really dead then it might take a a while to jump start. You may even have to rev the engine of the other car depending on what kind of car it is (how big of an engine it has). It is definitely over due for a battery so if the battery is not accepting a charge then the alternator won't be able to charge it. I would get a new battery, put it in, then get a multimeter and see if you are getting 14V at the battery with the car running. If your getting the 14V then the alternator is most likely good but you can still get it tested to be sure.

 
Rep Power: 0

Thanks! You gave me a bit of hope that it was just the battery, which seems to be the case. I got a new one and things seem to be going swimmingly -- I get ~12.6v engine off and ~14.6 engine on at the battery terminals.

I guess I was just really thrown off by the failure of the second jump start attempt; we even tried revving the engine on that one and it didn't help. We didn't leave it hooked up for long though, and while the donor car wasn't some tiny car, nor was it particularly beefy.

Didn't get the alternator tested though.