Last fall I wrote here how the resistor as part of a 12v conversion had died on my H after shutting it off in the yard. Same thing happened on my M yesterday while plowing my garden. I had make a couple of rounds when the tractor stopped just like I had turned off the switch. About 20 trips to the shop for the right tools, new connectors, bolts and fixing the wire to the switch after I pulled it from its connector and I was back plowing the garden again. I did both conversions back in 1988 so I don't know if I can really complain. One thing for sure if you have this kind of set up having a spare resistor should be in your tool box at all times. Only one left not changed is on my 300U. My other tractors all have mags so don't have to worry about resistors going bad.