Outdoor Power Equipment and Small Engines - 425 John Deere won't start

Our church has a 20 HP 425 John Deere for mowing the 3 acre lawn. It won't start. I used it about 3 weeks ago for the first time and all went well. The lights on the panel come on and I can hear the clicking of both the seat and brake safety switches. The PTO is disengaged. The fuel pump comes on. The like new oil is at the proper fill level. It acts as if a safety switch is not operating.
This mower was very well maintained for the 15 years we have had it. The man who mowed the church lawn for the past 25 years and maintained the mower was not feeling well and brought it to my father about a month ago to mow the church lawn until he could take care of it again. The gentleman passed away 2 weeks ago and "his" mower has not started since.
His widow has not been able to locate the owner's manual yet.

You say you hear the clicking of the brake and seat safety switches. Are you sure you are not hearing the click of the starter solenoid? What does it do when you turn the key....is it just dead, does the starter engage, do you hear a click or what? My limited experience needs more info:-)
I'm sure not familiar with that mower but I'm sure folks that are will be along soon and you will get the help you need.
Also - sorry to hear about your church member.

The first thing I would do is to put a meter across the battery and see what it reads. If it shows anywhere near 12 volts, keep it attached and try to start the mower. If the meter takes a big dive, replace the battery. Bad batteries often have enough charge to light the panel.

The clicks are after turning the key to the on position and lifting up in the seat then down to listen for the seat switch and then when depressing the brake peddle. We disconnected the seat switch and put in a jumper to bypass it but it didn't help so we plugged the wire back in to the seat switch. When turning the key to the start position, there is no sound. The lights on the panel and the headlights are bright so I don't think it is a battery problem. We did try to push the mower around a few feet just in case there was a dead spot in the starter.

PTO is disengaged, tranny is in neutral, foot on brake and someone sitting in the seat.... and nothing happens. Sure sounds like a safety switch is has crapped out on you to me. And you will have to check them all.

My usual go to for eliminating safety switches is remove the kill wire from the coil. My dad had a JD that sometimes needed the electric pto switch jiggled to start.....can you check for voltage at the solenoid during start and / or jump the solenoid to see what happens?

I can find no schematic on Deere's website to help me help you well. So, I suggest going to your local Deere dealer and ask them if they'd print one such up for you, if you can't find the manual, that is. You'll then need to perform a systematic check of the starting circuit beginning at the starter motor and working your way back to the battery using a 12V test light. My initial guesses are either: A control that is not truely disengaged; A bad starter motor; A faulty relay switch; A weak battery (you should have it professionally tested if you can't test for both voltage and amperage yourself); Or, a poor/corroded battery cable connection (six total - two on the battery, two on the starter solenoid, one on the tractor frame (from the negative terminal of the battery) and one on the starter motor.

If you receive ANY help from a Deere dealer without charge, I may as well begin preparing for the end of the world!
If the clicks you are referring to are from the switch themselves, than you still need to verify their operation electrically with a circuit tester/ohm meter. If each switch makes a click, say under the console, then you MAY be ok but verification with a meter should still be done.
You should have one small wire connected to a spade terminal on the starter solenoid (the solenoid is part of the starter itself) along with two big wires on lugs. You can check this wire for 12v with the key in the start position. If not, and your safety switches are verified, I would suspect the key switch and or module. This includes the key switch itself and a Printed Circuit board which I believe is hardwired and replaced as a kit which includes both. If you get this far I would then seek the deere dealer and see if they can or will test it for you since you will need a new part should it be the problem.

Thanks for all of your suggestions. There was a dead cell in the battery so I replaced it. While tracing the wires and cleaning them off I found that a wire on the front end of the starter had come off. I slid it back on and it started just fine.

thanks for the update.....that was kinda like missing keys...the last place you look...good deal.

The old guy probably pulled that wire off on his way "up", just to let folks remember who has been mowing the grass. Have a good one. Geo