Thanks, I will try and find all ground connections, although I do not seem to have a ground connecting to the base of the alternator.
I did clean and reinstall all ground connections I could find - and lo and behold the PTO and 4 wheel drive switches worked without killing the engine. Thanks for the advice... about five days later the whole thing started again - no dash lights on startup, engine starts fine until PTO or 4 wheel drive are engaged. I even connected the ground to my M 5400 and the oil pressure light came on after a minute or so, which indicates that all is good. Unfortunately, the next day the same thing, and this time connecting the grounds between the two tractors did nothing. I am starting to believe there might be some gremlins in this 8200 by-speed turn tractor... One thing all events when the PTO and 4 wheel switch ended up working again have in common was that the engine had been running for at least 10 minutes beforehand. This makes me wonder whether there is a relay or diode that does not work properly on start up but eventually comes online. However I am at a loss which relay to replace first? keystop relay, relay 1, or?
Any help would be most appreciated!
I bought this tractor a couple of years ago used, with a few hundred hours on and recently found out that a Kubota shop had previously dealt with this same issue and they thought they had fixed it.