My MTD Yard Machines tractor with a 21hp motor and a 46in deck will not start. It had been working fine up until recently. However, since our last rain it has not started. I cover it with a large tarp to make sure the tractor does not get wet as I do not have a shed or garage to store it in.

Now when I turn the ignition key nothing happens. I even disconnected the safety device that prevents the tractor from starting when no one sits in the seat. I checked the battery with a meter and it shows 12 volts. I also checked all the cable connectors and found them to be connected securely. At this point I do not know what else to check. Any suggestions would be appreciated.

I have the same situation with a MTD 22 hp, 46 in deck tractor. I had the click click click. And that stops quickly after a fresh battery. Stops for no clicking at all. Changed the battery . Which should be over 12.4 volts from what I've read so far. And the solenoid. Does anyone have any ideals ? Does anyone know if there is a fuse and where is it located ?

Just because the battery says 12 volts does not mean that it is charged well enough to turn the motor over.
One way to check the battery, while it is on the mower is to have someone help you, they sit on the mower, and make sure all of the safety switches are like they should be, the seat switch, the clutch, the engaged blade switch. After making sure about these make sure the mower is out of gear, now use a battery jumper cable and go from the hot post on the battery to the large post on the starter, if the battery is good the starter should engage and that would mean that you problem is somewhere else. It could be a loose wire in the safety system or a bad solenoid

Check Your Fuse.