wiring problems with MF 165 need help

our Massey Ferguson is having wiring problems. We moved it outside while we worked on the inside of the barn. It started Ok that day. (Not Great as we have always had trouble with it) we left it parked for several weeks. When we tried to start it....it went "click" and would not make anymore effort to start. The battery began to get hot. We tried to use a battery charger on it but it did not seem to work so we took it out and had it tested. It tested find and was returned to us with a full charge. We put it into the tractor and started to hooked it up and immediately it tried to start even though the key was in the off position, and the battery began to get very hot right away. We replaced the Key switch. We started to hook up the the battery and it began to get hot again right away. We carefully marked each wire and removed all the wires that went from the battery to the starter and key switch and safety switch and generator gage and the other gages that were tied together in that wiring harness. We checked each wire and found that all were good and had no resistance. we replaced a couple ends but the tractor will not start or make a noise. Does anyone know where we can get a wiring diagram and explanation of how the wires and gages work together etc.?

Sounds like the starter may have failed or is jammed against the ring gear and the solenoid has stuck.

Or the engine is stuck.

I agree with Bob,the starter is probably ingaged with flywheel. Remove inspection plate to see or just put tractor in gear and rock it back and forth to disingage starter.

How can that be? He said as soon as tried to hook up battery with the switch turned off it tried to start and everything got hot. If that switch was off how could the starter be causing that? Please explain that to me. Switch off should be no power to starter for it to act up.

BECAUSE!!!!! the little key switch turns on a bigger switch that is on the starter.. if that solenoid switch is stuck in the on position, it will be engaged all the time, no matter what the key switch is doing. That switch is mechanically tied to the bendix in some cases and if the bendix and drive gear a stuck on the ring gear, the starter is permanently turned on... till the bendix pops back in off position... rocking the tractor will unbind the ring gear and let the bendix pop loose... or it may require remove of the starter if the selenoid is bad or defective. And... as others said,, engine could be locked up to to mechanical problems and unable to to turn over..

Because little switch just operates a magnet in the solenoid on top of the starter which pulls a big washer that makes contact between the contact points of the big pos cable on the starter solenoid and starter. Sometimes the washer gets stuck to the contacts and starter keeps running. Happend to the neighbors massey same starter as yours. Hired man was driving didn't notice untill the battery got so hot it blew up.