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View Full Version : How to trace a bad ground/short - electrical systems


brown eyes
12-04-2005, 04:46 AM
Earlier this week I created this thread: Battery keeps draining - zenki S14 w/ KA24DE
Found here: http://www.zilvia.net/f/showthread.php?t=95768

The thread pretty much discussed why my battery kept draining. After some discussion, I was able to locate the problem with help from Ritz S14 and some other folks. I'm creating a new thread because I'm working on a whole different problem. Plus I hope this thread will get more hits and replies.

Ok now to the good part.

I followed these instructions as so delightfully illustrated by Ritz S14 and was able to locate the drain:

http://img.photobucket.com/albums/v648/br0wn_eyes/drain.jpg

The hard part is over, I diagnosed the problem. Now for the even harder step, isolating the source of the drain. I had a buddy of mine go into the driver side kick panel to start removing fuses while I monitored the light tester on the battery. Once he got to the 7.5a fuse for the "ELECTRON BATT", the light remained lit up for a few seconds, then it dimmed dramatically. We isolated the drain!

http://img.photobucket.com/albums/v648/br0wn_eyes/fuseblock2.jpg

Next step now is to trace where the "ELECTRON BATT" fuse leads to. This will require the wiring diagrams from the factory service manual. After a hour of searching, I found this diagram:

http://img.photobucket.com/albums/v648/br0wn_eyes/fuseblock.jpg

As you can see, the fuse is linked to systems in the car that remain on even when the car is turned off. Functions such as the horn (so you can honk when the car is turned off), audio (a bit of power goes into that so it would maintain the programming memory stored into your head unit), power antenna (so the antenna would roll down when you shut off the car), theft (my S14 is an SE and is equipped with a factory theft warning system), a/t (not sure what this stands for, I'm assuming automatic transmission, which doesn't apply to me) and finally abs (which doesn't apply to me either because my car isn't equipped with it).

I do have an aftermarket headunit which I installed a long ass time ago and I'm pretty sure my wiring was done correctly. It was so simple and I maintained all the harnesses. It might be my alarm system, the guy who installed it might have tapped into something he shouldn't have. However, all these things were installed a long time ago, so it would be strange that a problem such as this would surface this late. Possibly my power antenna, it's been acting up lately; sometimes it has a tendency to jam up and not roll all the way down. It could be my horn, I did get into an accident a year ago and since then, my horn has been disconnected. It could be the factory theft warning system, those things have a tendency to crap out after a while.

Here's the tricky part. How do I even begin to approach a problem such as this? Its like a needle in a haystack. I'd hate to start tearing into things and I'm not certain where the most logical place is to begin. Anyone ever encounter a problem similiar to mine?

So far, I've been pulling the "ELECTRON BATT" fuse everytime I park my car for an extended period of time. Its a temporary fix to avoid battery drain, but I can't keep doing it. HELP~!

rrobe99999
12-06-2005, 01:47 PM
You're getting there. Now you just have to figure out which device on the circuit is causing the drain. Continue your approach by pulling the fuses at the radio and alarm. Its probably not the horn, since its disconnected. Whenever I've had a drain, it's always been a bad ground on something that I installed. Sometimes chassis grounds can loosen or become corroded over time.

ledzeppelin240
12-06-2005, 09:18 PM
A bad ground will not cause a drain, you have a short to copper. A short to ground usually blows a fuse due to the increase in current, as a short to copper may or may not blow the fuse.

Keep in mind that there will be a slight current draw from the battery for the ECM, head unit and stuff like that. But from what you have said you are aware of that. I would start by now disconnecting the power side of the circuits that are run on that fuse. The test light will go out when you have diconnected the circuit that is causing the drain.

An acceptable drain on the battery is 20-30mA with a max of 50mA.