GM-GMC: electrical problem on 1998 Chev. 2500 diesel, amp fuse, light fuse

Question
Harry, I have been having a problem with a batt. drain on my truck.  It has a duel batt. system with remote start and a myers plow. It has emer. lights and an add on back-up light.  About 3 months ago I had a problem with the shift bracket (the plate broke and I had to replace it)  It was during this repair that I noticed the batt. went down.  At first I thought it was just the #2 batt. because it was about 5 years old (I replaced the #1 about 6 months ago).  But the problem is still happening.  When I disconnect the #2 batt.(passenger side)  and pull the light fuse (50 amp) the drain stops.  If I reconnect the #2 batt. it shows a drain again.  If I have the #2 batt. disconnected and then put the light fuse back in - it shows a drain.  Any ideas or have you had this problem before.  As I said, before the shift plate repair, no problems like this.  I went back over my work to see if I missed anything (wires , etc. and could not find any problems.  Oh, I did find one of the light wires for the plow hook-up was exposed and touching on the bumper around the time I started to have problems.  However it did not blow any fuse but I did notice a small discoloration on the chrome where the end of the wire touched it.  An yes, I was dumb because I did not disconnect the batt. before I did the repair on the shift plate.  I can't think of any other pertinate infor at this time.  Thanks for any ideas or help you can give.  

Answer
Bob,

The problem is obviously in the circuit which the 50 Amp fuse protects.

You will have to trace all the wiring to its end for that circuit.  Somewhere along the way, you should find a place where the insulation is bad or a device that is drawing current when it is supposed to be off.

The #1 battery (driver's side) should have a ground to the engine and a positive cable to the positive terminal on the #2 battery.  You should completely disconnect the #1 battery (remove all connections from the battery itself) and confirm that the drain is on the connection/fuse when powered by the #2 battery only.

You have isolated the drain circuit.  You now need to find out what is causing the drain.