I have a JD750 and the previous own has rewired the electrical system and added a solenoid on the firewall. Anyone have any idea why they would have done this?
Probably for an accessory, like an extra light maybe? Or maybe something to do with the front or mid PTO, if it has that function? Can you trace the wires to wherever they go? That should tell you.
Just a guess, but I think it could be for a starter "fix" that some of the folks were adding to the 750's to aid starter performance. (Read about this somewhere a while back)
I don't know about the starter but I bought a cab and it came with a solinoid that was used to run the extra lights, wiper and heater. Follow the wires and you'll know in no time.