Purchased TYM 273 in 2008. We have been maintaining (including having the frame welded when it split in two - seriously!) The issue is that when the key is turned to 'start' the tractor starts just fine and if you HOLD the key in the Start position, you can drive it - keeps running. As soon as the key is released and returns to the 'run' position, the fuse blows. The fuse that blows is the EO/PTO 20amp. We replaced the starter, we found 2 different wires that were 'exposed' and wrapped those in electrical tape, We unhooked the wiring harness for thermostat, removed the PTO relay, tried disconnecting the alternator. I believe we unhooked the wiring harness for the fuel injector. All of these (according to other posts) and tried to start and yet the fuse keeps blowing. We also reviewed this blog about the wiring harness under the dash https://www.tractorbynet.com/forums/tym-tractors/338284-273-died.html?highlight=tractor,+TYM,+fuse and I think that is next to check although we had the dash off and didn't see anything. There are several comments regarding "safety switches" but we are not understanding where the 'safety switches' would be - our seat doesn't have a pressure release that we know of (when I get off it keeps running) - I am not aware of any safety related to the PTO but if someone could be more specific, that would help. It originally just 'stopped' running when I was moving some small rocks for my neighbor - just using the bucket, no PTO. I had driven a ways down the road - an thought maybe a wire had grounded but we have had no luck finding a loose wire. The odd thing is = it runs if you keep the key in the "start" position and only blows the fuse when the key is released to 'run' - which is handy as we were able to load it and return it home (no blocked driveways etc. 
) Please, anyone have any ideas? Even the dealer was stumped.
) Please, anyone have any ideas? Even the dealer was stumped.
