Parasitic battery drain dead out of nowhere?

STEVIENIX

MEMBER
2005 SATURN VUE
3.5L
V6
2WD
AUTOMATIC
240,000 MILES

Recently, my battery was dead out of nowhere. I replaced the battery because it was older just in case. Now the battery drains down in one or two days of sitting in the driveway. When I remove all of the fuses in the fuse panel, I do not see a draw from the battery when I touch the cable to the post (it does not spark). When I install the 40 amp main fuse that feeds the entire circuit board and with no other fuses installed, there is a pretty good spark when I touch the cable to the battery post, and the battery will drain down. Also, I have the other cable that goes to the starter disconnected. Not sure where to go from here to identify what is causing the battery to drain?

Friday, December 19th, 2025 AT 10:45 AM

1 Reply

STEVE W.

MECHANIC
15,314 POSTS

OK we need to narrow down the actual circuit as there are multiple fuses that could be the issue. Do you have a test light or a meter to test with? Is the fuse you pulled the one labelled Batt Feed? That one feeds the interior fuse panel. These diagrams should cover all the fuses. For testing you will need three items. A large 30 amp ammeter like you would install in the car, a smaller multimeter that has at least a 10 amp amp rating and a pen.
The pen will be used to trip the latch on the door so that the switch in the lock stays off.
Then connect the large current ammeter between the battery negative post and the negative battery cable. Leave the key OFF (this is because you don't know the extent of the short yet, if it is over 10 amps it will blow most of the common multimeters fuses or circuits while it won't damage the larger meter)
Now with it connected install the fuses in the under hood fuse box one at a time. Skip the 40 amp for now. If one of them causes the meter to jump up, wait a few minutes to see if it goes back to sleep, if not write down the number and move to the next one until they are all back in. Now if the meter is on zero or very close to it, disconnect one side and connect the multimeter in the circuit with it on the 10 amp or higher setting and write down the amp draw (if any). Now disconnect the meter and re-connect the larger meter. Plug in the fuse that is the problem. If it's the one that feed the interior box great. Note the reading. Now go to the interior fuse panel and pull the fuses there until the draw drops. Note that fuse and put it back in, keep going until you have pulled them all. Now you should have one or two fuses that caused the load to stop. Either look on the diagrams for the fuse number and what it feeds or reply back with it and we can continue. Common ones that cause a draw are the BCM, the radio (especially aftermarket) fuel pumps and lights.
Now you just need to follow the draw and the circuit. The last images are what each fuse actually feeds. Do some testing and see what you find, then we can see about fixing it.

Brian does a good demo of a parasitic draw test on a Ford, but it applies to any vehicle.
https://www.youtube.com/watch?v=6xFo_oHFF48

Now if you have a thermal camera available you can just look at the fuse boxes and find the hot fuse or relay.

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