I'm having some issues with my wife's car and I'm not exactly sure what the problem is, so I was hoping you guys might be able to give me a little insight. When I go to start the car, it turns over noticably slower than normal, but it still starts. The headlights also dim when starting. My initial reaction was that there was something wrong with the battery, but I checked it with a volt meter and it seems fine, I think. I'm not 100% positive on how to use the volt meter though. I set it to 15 AC and when I touched the contacts to the terminals, the needle went all the way up to 15. I know the battery should be producing like 12 or 12.5 volts, which leads me to believe that I was using the volt meter improperly. I thought maybe the battery was low on water, but when I looked at it I realized that its a sealed battery, but it does have a built-in hydrometer which was reading green (ie good). My other thought was that maybe the alternator wasn't charging the battery properly, but if the alternator was putting out less than 12v then wouldn't the alternator light come on? My last idea is that its some kind of wiring or grounding issue, but what exactly, I don't know.

Anybody got any ideas, or suggestions?

 

without your car running the battery should be atleast 12.45v and with the car started it should be steadly at 13.5 to 14.2 volts...if its lower than 12.45volts before you start the car up try to charge it up for about 1 hour if you've got a battery charger or if not start your car and let it self charge for about 15minutes and turn if off for about a minute and recheck your battery voltage...but if you start the car up and it reads in the 12 volt range you could be having a problem with your alternator or wiring somewhere...if it's higher than 14.20volts you have a voltage regulator issue...hopefully the info helps you a bit...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by brentmc79 &raquo;</TD></TR><TR><TD CLASS="quote">... I set it to 15 AC ...</TD></TR></TABLE>Car electrics are DC. Set it to 15 Volts DC or a similar range like that.

Like brent says, it should read above 12 volts just sitting there. But I'm afraid to say something as precise as 12.45 because some inexpensive meters can be pretty far off. It's better to compare how the voltage changes when you turn stuff on & off.

Now try a couple other things...

1) Engine off, battery voltage, just so we know for comparison.

2) Engine off, turn on all your headlights, stereo, ventilation blower, whatever. Battery voltage should not drop below about 12.

3) Same test with stuff turned on, but instead of putting the meter across the battery posts, this time put the meter from some big terminal at the fusebox to a good ground on the body.

4) Turn the stuff off. With the meter probes on the battery posts, start the car. While the starter is operating watch how low the voltage drops.

5) Battery voltage with the engine running.

6) Engine still idling, but turn on all the lights & stuff you can.

Tell us what each of these tests gives, but here's some ideas.
If #2 is much less than #1, battery isn't real good.
If #3 is much less than #2, you have a loose/dirty/corroded battery cable somewhere.
Normally, #4 might be as low as about 9v.
If #6 is lower than #5, alternator is weak.

 

I appreciate the info, but now I think it was actually just the weather because it was really freakin cold last night (~20). I let it sit all day today and tried to start it again tonight. It turned over a little slow but it still started right up. Its due for an oil change, so I'll probably try a lighter weight oil.