Tractor Repair: JD 4310 electrical problem, epower, key switch

Question
Hello, I have the JD 4310 epower reverser, the engine quit while mowing, and now the 20 amp key switch fuse keeps blowing when I turn the key, however, if the MFWD switch is "ON" the fuse does not blow and the tractor runs fine.  Ive only used the MFWD when Ive needed it, usually mow in 2wd.  Ive run the wire harness, cant find an open.  Could the problem be in the MFWD switch itself?  A relay before the fuse?  Running out of ideas.  Thanks!

Answer
You most likely have a mfwd solenoid shorted out. When you turn the switch on, power to the solenoid is turned off. The mfwd is mechanically applied with a spring and electrically over hydraulic disengaged. Unplug the solenoid which on the right side middle of the transmission. Its in a block with one or two other solenoids. If you have and ohm meter you can check resistance across the terminals of the solenoid. It should be around 8 ohms. If that tests ok then you have the wire that supplies power to that solenoid shorted to ground. You can swap the solenoids to make a quick check.