I have a 20hp. 42 in. mower, when I turn the key

hello sir, The clutch safety switch will kill the engine when the clutch/brake pedal is released. The deck switch will kill the engine when the blades are engaged. The seat switch will allow the engine to run when the rider isn't present. when the parking brake is set. instead of killing the engine when the rider isn't present. They don't usually give you any warning they just quit. You can check the safety switches if you make a jumper wire to use to complete the circuit. This will help determine which switches are bad.hope this helps, MrFixIt, oh could you please rate this solution,thank you~~~