How do I go about finding out why my battery is getting drained?

[BlueOvalStangGT]

I've had this problem for a couple weeks now, when I leave the car over night or for an extended period of time, the next morning the battery will be dead. I now have a volt meter and when I hook it up the voltage does go down slowly when the car is off and no lights on or anything. How do I start to trouble shoot this problem?

 

[bjl95mustang]

I think this will work.

Set your meter to ohm with tone. Make sure everything is off and unplug the hood light. Disconnect the batt cables then connect the ohm to either ends of it. If it tones then it's grounding out the + side. If you have some clips, clip the meter to the cables and start playing with wires ect.

I hope this is a start.

 

[BPA]

You need to do a draw test.. conector your meter up so its using amps. anything more than .05 amps is exesive. make sure u have ur hood light and key out and off. u can find out what system is causing the drain by unpuging fuses..

 

[HISSIN50]

I do it like BPA. Dont forget that if you find nothing otherwise, to disco' the alternator cable and note a reading delta, in case you have a bad diode in there (this sounds like a large drain so that could be it).

 

[mo_dingo]

I think this will work.

Set your meter to ohm with tone. Make sure everything is off and unplug the hood light. Disconnect the batt cables then connect the ohm to either ends of it. If it tones then it's grounding out the + side. If you have some clips, clip the meter to the cables and start playing with wires ect.

I hope this is a start.

It will always tone, because there are lights hooked up. You would have to remove all light bulbs to test it that way. Light bulbs in any circuit will show a short to ground, except that it will have a few ohms resistance, not zero.

You need to get a DC amp clamp and put it on the pos battery cable and see what reading you get (with everything off). An ammeter gauge will work too if you disconnect the pos. lead at the battery and put one lead of the gauge at the cable and the other at the battery.

If you don't have a bad drain on the battery, you likely have a bad battery. Get it tested, as well as the alternator. The alternator should put out 14.4V AC if you want to test it yourself.
Scott

 

[BlueOvalStangGT]

The battery was under warrenty so I replaced that along wiht new terminals. The alternator is charging my battery fine, if i did the test right. I know wit hthe car running the volts from the battery are higher then with the car off. Somone said sometihng about diodes draining it, thats what my dad told me it could be. How do I test if the alternator is draining the battery?

 

[mo_dingo]

The battery was under warrenty so I replaced that along wiht new terminals. The alternator is charging my battery fine, if i did the test right. I know wit hthe car running the volts from the battery are higher then with the car off. Somone said sometihng about diodes draining it, thats what my dad told me it could be. How do I test if the alternator is draining the battery?

The diodes convert the 12V AC output of the alternator to the 12VDC that the battery gets charged from.

You need to see how many amps you are drawing w/ everything off. A DC amp clamp or a ammeter will tell you. Most multimeters will not read anything higher than 200ma. The most I have seen is 20. So that is why a ammeter or an amp clamp would work best.
Scott

 

[BlueOvalStangGT]

Where can I get a ammeter? Ill post pictures of my multimeter tomorow as I dont know how to use it very well and I dont exactly know what you guys are talking about.

 

[BlueOvalStangGT]

Can anyone help me? Heres what my DMM looks like, can I use this?