i have an 04 mustang gt and i just put a battery relocation kit in. i grounded the negative terminal under the hood to the frame, connected the power wire to the old positive terminal that is under the hood, and grounded the battery to inside the trunk. started it up and it worked fine. then over night the battery drained. there must be a short somewhere because it keeps draining everywhere i drive it. i checked all the connections and they are tight. im very confused. any help is appreciated. thanks.

 

You need to find out what is drawing the current. I normally hook up a current meter(in series to one of the power wires) and then start pulling fuses one at a time to see when the current draw stops.

I would start simple though and even though you are sure all the connections are good, remove them, clean and then re-tighten them. A bad connection can cause this, or a bad ground in the trunk. You scrapped the paint right?

 

You know you don't really need to ground the old ground right, you could have just secured it, that wire only runs to a.... well, ground obviously.

Hook up a multimeter to your terminals and start pulling fuses, I would start with the bigger ones under the hood, then if you find no change in current draw, move to the ones under your dash.

Constant draw should be around .060 - .012 depending on vehicle and if you have an alarm and so forth. Once you locate which fuse is pulling all the power, get in your chilton/haynes whatever and see what that fuse controls and troubleshoot from there.

I had a drain of about .28 at one time, it was my aftermarket alarm I had on the car that was on it for over a year and it suddenly started doing it, dont know why or what made it start doing it cause the place I worked at took care of it for me, so if your sure you ran everything correctly, don't instantly assume it's the job you did. it really could be anything so keep an open mind.

Pretty much the same as far as what ttocs said...