How to check for battery drain?

car noob said:
Put a test light in series with the positive cable, or put a DMM on one of the cables



and if it lights up when theres supposed to be NO battery draw you have a short... make sure the interior light is off and ignition off..... then start unpluggin things as a process of ilimination... such as start with the fuse box then unplug the alternature... etc.....

-gbm-
 
OK, I've got a Volt meter (is that basically a DMM?).
Where do I actually take the voltage reading?
Do I read right off of the positive battery terminal?
Do I leave the battery grounded or remove the ground connection?
Will a short verses a drain regester differently?

Thanks, I just need a little more guidance with electrical issues.

Tim
 
You need to measure the CURRENT between the negative post of the battery and the disconnected negative lead. Your volt/ohm/current meter should be rated for 10 to 20 amps DC current. IIRC 10-30 milliohms for items like radio, clock, etc that are always connected. If you have an alarm or other items that have a constant connection you may see up to 120 or so milliohms. If it is radically above that then you have a short.

Hope this helps
 
What GP001 said, except replace "milliohms" with "milliamps"

A normal current draw for a classic would be about 0.2 amps (200 milliamps).
A Classic with a bunch of electronics (aftermarket stereo, alarm, etc) could be as high a 0.8 amps. You should definately see a drain of less than an amp, and preferably less than 1/2 of an amp.

Like GBM said.. start pulling fuses until you see the current drain take a large drop. This way you limit the problem to a single circuit.
 
Or you could hill-billy it.

Pull the positive cable with the car in a garage that can be darkened completely. Then touch the cable to the post. If you see a spark, you have something draining. This wont tell you how big the drain is, but will tell you if you have a draw.
 
Cantedvalve said:
Or you could hill-billy it.

Pull the positive cable with the car in a garage that can be darkened completely. Then touch the cable to the post. If you see a spark, you have something draining. This wont tell you how big the drain is, but will tell you if you have a draw.

That might not work so well. In my car I have alot of stereo equipment with alot of capacitance in the electronics. In this case, lots of current is needed for a split second, then very little is used at all. I literally flinch every time I connect the main power or ground cable, yet my car doesn't have a power drain problem.
 
Do you leave the battery cable on all the time ? For some reason when you move the bat to the rear this happens. I had this problem with my last car. I put a turnoff switch on one of the cables, it has a wire so it hold memory for radio, clock and that type stuff. After that my problems were cured. No more drain problems.

any pics of how you mounted the battery in the rear of your car ?
thanks, hope the info helps
brian