Ford Repair: 1986 Ford F150, positive cable, ford f150

Question
I have a 1986 Ford automatic F150. It is 2 wheel drive and has a 351 in it. I have a problem with the battery slowly draining with truck turned off. After a day or two it will drain battery completely. I took the positive cable off and rubbed it on the terminal with everything turned off. There was a spark and clicking noise. The clicking is coming from a small box mounted on the firewall on drivers side. It has a plug with sveral wires going various places. Is it the box that is causing battery to drain or could this be something else? Thanks for your help.

Answer
Hi troy thanks for asking.
This may not be the problem the best way to check for this problem it to get a multi meter that measures amperage. disconnect one of the battery terminals and connect one lead to the terminal and one lead to the battery. If there is a draw there should be a reading of over 1 amp. start disconnecting items that you may think the problem is coming from. when you disconnect the part causing the problem the amperage will drop to almost nothing.. there will be a litlebit of draw because of things lick you clock on your radio ect... this is the easiest way to find a drw problem.
Chris P