My wife was mowing with our John Deere 425 tractor and she mowed about a half hour when the mower quit running. She tried to re-start it and..nothing. I went out to make sure she didn't leave the PTO switch on and she didn't. I tried to restart it and it wouldn't do anything, not even click. I tried the lights and they worked fine so don't think the battery is dead. Where should I start checking? I'll make sure the (new) battery is up and has good connections but since the lights work I guess it's something else. Thanks in advance for your help.