I need your input. Battery or alternator?

[fudge12]

This morning my LS started on a dime; half crank and she was running. Went to work and when I came back out on lunch to go home (approximately sitting for 7 hours), it barely started; to the point where the gauges would rotate all the way up and back down but it started. It's approximately a 15 minute drive from work to home and I'm pretty darn sure that's more than enough to start the car 45 minutes after I turn it off. After finish eating lunch, the car cranked slowly and quit.

00' v6, no battery indicator or anything of such came on, other than the usual advancetrac, air bag light, and bulb out light. I'm not sure if it's related to this, but for some odd reason the right brake light bulb always bursts (yes, shatters into pieces) within a week of replacing it. I got tired of buying bulbs since I probably can save up the amount of money I waste on bulbs and use it on a damn ticket.

Would your bets be on a battery or alternator? As is, my battery is reading 9 volts and that's after one crank and quit.

 

[joegr]

More information is needed. It could be the battery, the alternator, a parasitic drain, or some combination of the three. You need to make some measurements.

1. With the engine running (at idle) what is the battery voltage?
If it is less than 13.8 or more than 14.8, you have a problem with the alternator (most likely), the wiring, or the PCM (least likely).

2. Assuming that test 1 passed, after the engine has run for at least 30 minutes, turn it off and measure the battery voltage right then.
With a good battery, it should start at 13.8V and drop down over a few minutes to 12.6V. If it quickly goes below 12.6V, you have a bad battery.

3. If you passed tests 1 and 2, then wait a couple of hours and measure the battery voltage again. If it's below 12.3, then you have a parasitic drain or a bad battery. Take the battery and have it load tested to figure out which one it is. Pray it's not a parasitic drain. Those can be hard to track down and correct.

On the bulbs:
Do they burst some time after a rain or a car wash? I would suspect that water is getting in and splashing on the hot bulb.

 

[fudge12]

If my memory serves me right, i would have 13.9v -14.1v (max) when the car is running. This was a week ago when I had the volt meter attached. When I turn the car off, it would drop to 12.1 - 12.3. When starting, voltage drops to 10.9v (lowest). It usually happens when it rains, but I made 4 micro holes per side to let water out since last month. Now I have no water in the housing, but it still bursts.

Parasitic drains don't really bother me since those aren't too hard to find for me. I deal with them every day at work.

 

[jrand]

bulbs were probably just junk. i bought sylvania bulbs and went thru like 3 in a matter of a week but have had the same one in there for over two years now.. also a sylvania. how old is your battery?

 

[fudge12]

bulbs were probably just junk. i bought sylvania bulbs and went thru like 3 in a matter of a week but have had the same one in there for over two years now.. also a sylvania. how old is your battery?

Sylvania bulbs too. The battery is just 2 years old. Im out of warranty by 2 days.

 

[jrand]

might want to try the warranty anyways, maybe they do the math wrong and think youre in warranty.

i dunno what caused my issues with that light, but i did take a good shot on that end of the car when i totaled it <i rebuilt>. i got a new socket when i got a new light. i dunno which socket i have in there now , the new or the old, but i think it was just junk bulbs.

 

[Telco]

Parasitic drains don't really bother me since those aren't too hard to find for me. I deal with them every day at work.

I'm going to suggest that you go ahead and track this down then. The BRAKE LIGHT CIRCUIT is active at all times for safety reasons, not just when the car is turned on. It's possible that there is a short that is blowing the bulb, and this short might be draining your battery off. If it's getting worse, that would indicate that the short has gotten worse. If it's draining the battery off, then the alternator's going to blow trying to recharge a low/dead battery. If it doesn't fix the issue, you can at least eliminate it as a cause.

 

[fudge12]

I'm going to suggest that you go ahead and track this down then. The BRAKE LIGHT CIRCUIT is active at all times for safety reasons, not just when the car is turned on. It's possible that there is a short that is blowing the bulb, and this short might be draining your battery off. If it's getting worse, that would indicate that the short has gotten worse. If it's draining the battery off, then the alternator's going to blow trying to recharge a low/dead battery. If it doesn't fix the issue, you can at least eliminate it as a cause.

Indeed that makes sense. While I can't find any parasitic drains, I am going to replace the socket. A new battery seems to have remedied the issue however.