Need help with battery issue

[5.0_GT_kid]

Yesterday afternoon I went out to go get some lunch but my battery was flat out dead. Well it was an older battery and on it's way out so I knew I should just buy a new one. I went and picked one up and, got it installed and it worked fine. This morning about 6am I had to take my little brother to work and the car ran fine. I came back home and had to leave for work around 11am and the car wouldn't start. Now I double checked and I didn't leave the lights on or anything else that I can see, so something is putting a drain on my battery I assume.

Can anyone point me in the right direction.

 

[wytstang]

First make sure everything of off. Grab a test light connect it to the positive side, touch the negative side. If it lights up something is drawing power. Start pulling fuses until the light shuts off. When it does you have an idea of what accessories might be drawing power.

 

[HISSIN50]

You need to disconnect the negative battery cable. Put your DMM in-series between the battery cable and battery post. Set your meter to read amperage-draw (most meters can only handle about 10 amps so don't turn on anything that draws a lot of power or you'll blow your meter's fuse or melt the meter down).

Close the doors, remove the underhood light if you have one, and note the reading. It should be under 100 mA (0.1 amps) as I recall. Now start pulling fuses till the draw (reading) goes down. If that doesnt work, disconnect the alternator to see if that drops the parasitic draw.

Things like glovebox doors, vanity mirror lights, trunk lights, etc are common issues that cause a draw.

Good luck.

 

[5.0_GT_kid]

Thanks guys I'll check that tonight

 

[mo_dingo]

Also, with the car running check the battery voltage. If it's not at least 13V you should start looking at the charging system.

FYI, using a test light to check amp draw is pointless. Your computer, radios, etc. will always drain the battery slightly. A 1 amp draw will completely drain your battery in 4 days (assuming 100 a/h batt). A 1/10 amp draw would be around 40 days.

JT is on the right track.
Scott

 

[bmac50]

Check all your grounds and make sure there's a good connection.