Battery drain problem! NEED AN EXPERT?

Question

Ok look heres the problem I need an expert :P
Ok first the battery is draining rapidly. The alternator is good the battery is good. I can jump it it runs then it dies 2 minutes later.So I bust out the multimeter: + to - its 12.0 - to Alternator is 12.0. So then I disconnected the -, ok so - on the battery to the - cable is 11.9. So is there power running on the - cable ?

Next I did this hooked the - back to the battery then I ran the - on the multimeter to the chasi of the car (like the side of it the engine different metal areas) and i'm getting a .1 reading on the multimeter. Some areas it wont do it some it will.

Now the odd thing is the - on the battery to the - cable I was getting 11.8 - 11.9 and now with the - cable hooked to the battery and the multimeter - to the battery and + to a chasi part i'm getting .1?

Sorry if this is hard to understand BUT PLEASE help its driving me nuts!

Answer 1

If you only have 12v across the battery when the engine is running, your alternator is not doing its job. You should at least see above 13.5V at a high idle, and probably closer to 14v.

The .1v difference you are getting in the cable is of little consequence.

Answer 2

You should be checking for amperage draw instead of voltage. Of course you failed to mention the year, make and model of car in question, but if it is newer than a 1985, it has a computer that draws power all the time, so you'll always see battery voltage when you test like you did. What makes the differrence is the amount of amperage that it is using.
So, hopefully you have a multimeter with a 10 amp setting. Disconnect the positive battery cable and connect the multimeter between the battery and cable. With the door closed and ignition off, you should see less than .5 amps. If the reading is more you have an unacceptable draw, and it needs to be located. Remove the interior light bulbs and start to remove fuses, one at a time (keeping track of where they go) until the meter reading decreases or goes away. Note that when the computer fuse is removed the reading will decrease somewhat unless it is the cause of the drain so remove it first. Once the fuse of the circuit where the problem is located is removed, the high amp reading should go away. That circuit will have to be inspected for damaged wiring, shorted components. Note that the alternator can be charging good and still have a bad diode that allows current to be pulled from the battery so disconnect all the wiring from it first as a quick check. Hope this get you started in the right direction.

Answer 3

A fully charged batt. should read at least 13.5 volts.If you are reading 11.9 volts across the neg. cable to the battery post you have something drawing current. The neg. should read 0 or maybe .0.2 or so. Something is turned on.

Answer 4

sounds like you have a bad electrical connection SOMEWHERE in your charging circuit

Mechanic is the best answer here.........the charging system needs to be traced and the connections tested.

Don't waste your time here!

Answer 5

You need to take it to an auto electric technician if you want the expert.