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Old 11-17-2012, 02:22 PM
robertobaggio20 robertobaggio20 is offline
Location: earth
Join Date: Oct 2009
Posts: 3,403
Mein Auto: car
Originally Posted by paperplane94 View Post
The way to check for battery drain is as follows, get an ammeter, or a DMM that has an ammeter setting.

Remove the backseat bottom and roll down your rear windows so you can access the fusebox without opening the door.
Remove the negative cable.
connect the ammeter between the neg. cable and the negative battery post.
Wait a few seconds for all the electronics and check control to shut down.
There should be a small battery drain that is used for the clock, about less than .03 amps
Anything more than that value....begin by pulling fuses in the front, then rear fusebox while watching the ammeter for a drop in current drawn.
If the current comes down to less than .03 amps you have found the circuit draining the car!
ID and fix circuit accordingly.

Well, I can now positively confirm that there is no need to remove a battery terminal and hook up the ammeter in between, and no need* to pull out and replace fuses one by one.

I just tested this on my car. Switched the digital multimeter to the 200ma setting, and place both leads on each exposed end of the top of a fuse you're testing while it still fixed in the fuse box. In this case, I used the luggage compartment or boot. I opened the boot and its internal light came on. The reading was around 13.5 when the car was running and 12.5 when it wasn't. I closed the boot. The reading was zero when the car was running and zero when it wasn't. So that makes sense.

When you identify the fuse that is drawing current, if the description in your fuse box indicates a component that should not be functioning when the engine is off and the key removed, then you've found your current draw. Please check the component's wiring, relays, and/or replace the component itself. If the fuse box's description indicates a group of components, then you'll have to check each component separately for current draw at the component/component's dedicated circuit alone, to isolate the actual culprit.

Please take note that voltage cannot be tested this way. For voltage to be tested, you need to connect one lead to the fuse and the other lead to an earth point, usually a nut on the shock absorber tower for convenience. Of course, the multimeter needs to be switched to 20volts to permit this. Current draw cannot be tested this way....both leads need to be on the fuse itself. My head hurts so I can't explain why right now.


* Emphasis added as the need to unfasten the batt terminals and pull fuses clearly seems to be a common misconception even amongst experts. No disrespect intended.

Last edited by robertobaggio20; 11-17-2012 at 09:00 PM.
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