One of my buddies had me look at his dads truck, its a 2004 6.0, and they were having problems with the batteries draining and having to jump start it everytime. About a month ago they took it to the dealer and the dealer ran there tests and changed out both batteries. The truck ran fine for amonth with no issues and it started doing it again yesterday. The batteries and alternator are good. I glanced at the fuses real quick and one of the big 20amp fuses for the trailer tow battery charge was blown. Has anyone ever seen this fuse being blown and cause the batteries to drain. The way it was blown it was still making contact alittle, so I am thinking it might be arcing and shorting out draining the battery. I told him to leave the fuse out for a few days and see if the problem stops, but he wanted to just replace the fuse now so he wont forget to put it back in. Any info on this. Thanks.