hey there i just started having a problem i noticed on sat morning when i went to start my car , i noticed the battery was quite low and it didnt start.
i got a jump start and then it started up and worked the whole day, so im thinking its not the alternator because it worked each time i started it during that day, but then the next morning it didnt start again and the battery was dead, so im thinking something must be draining it somehow, but it just started out of nowhere, i havent changed anything recently.
i did a battery load test at my work, and it passed at like perfect, since its a month old battery.
now electrical wise in the car all i have is my alarm, radar detector, and stereo, but each night i always set the alarm, take off the faceplate, and take out the radar detector, and im not leaving my lights on although lately i have been having a problem with the headlights going down sometimes, like they wont go down if i have already turned off the ignition, but thats not the current problem at hang, i wonder how or what could be draining the battey so much, it doesnt drain all the way to empty, just enough for it to not start.

 

Try taking the neg battery cable off while it is running. If it dies then your alt has taken a crap, if not take it to a parts place and let them test the charging system and starting sustem and go from there.

Also could be a bad ground somewhere.

peace

 

Do what damon mentioned with the neg cable.

Plus make sure your battery wire cable connectors are in good condition. A lot of the times the wires are original and the ends need to be retrimed and mounted again. Also, make sure there is not build up around the battery terminals.

-Error402

 

use a volt-meter set on AC voltage and see how much alternating current is occuring at the termals. This will tell you if your diodes are ok. If it jumps a bunch from idle to 4000rpm, you got a bad diode. Also set the meter to DC and see how much the voltage changes from idle to 4000rpm. It should remain between 12.6-13.9volts, if it goes all over the place, its likely your battery can't hold a charge anymore.

 

but the battery is fine, they did a load test on it for me
im going to go back to work in about half an hour and ask them to do an alternator test for me
if that turns out ok
then its time to start usin the voltimeter and taking out fuses etc...
thanks

 

To me, it sounds like a classic case of shorted cell within the battery. Disconnect the battery when you shut the car down for the night. Reconnect it in the morning. If the battery is dead - odds are it's a bad battery, regardless of age or load tests. If it's nice and hot, the problem lies elsewhere.

 

ok i did that... battery is fine, seems as tho alternator is fine as well, so something must be draining battery, possible headlight switch maybe?

 

If it's a month old, take it back and exchange it.