Small Engines (Lawn Mowers, etc.): Craftsman riding mower wont start, craftsman riding mower, electrical diagram

Question
I recently "inherited" a Craftsman riding mower. I was told that the battery is less than two years old. It required a jump with a battery chrager in order to turn over and start the motor. Once fired up it runs nicely. However, there is some sort of electricla problem, because it will not start itslef up. When turning the key (yes the brake is engaged and the seat switch activated) there is complete silence. No attempt to turn over, no clicking, no anythin. We ran it for about 30 minutes, but after shutting it down it just doesn;t seem to have charged enough juice to start itslef up. I have the owner's manual and it shows an electrical diagram. My guess is that besides the battery there could be an issue with the alternator or charging diode (as indicated in diagram). This tractor is worth salvaging, and I don;t mind getting dirty to do so.

Can you give me some troublshooting advice? The model number is 917.257660.

Thank you so much!  

Answer
Hi Lenny,

I suspect the battery also.  Charge it with a charger and check for good cranking.  If normal on board charging is the only problem we can address that.  See my No Cranking troubleshooting below.

I would check the starter first.  Jump the positive battery terminal to the starter and it should crank over. If so, skip to step 2.
If not, jump from a battery that you know is good, from a car.  If still nothing, the starter is bad.  If good, then the mower battery is weak.  

Step 2.
If the starter and battery are good, you will need to trace the entire circuit from the starter to the battery.   The solenoid, switches the battery power to the starter, when power from the key switch is sent to the small terminal on the solenoid. To test the solenoid, first make sure that you have power at its large terminal which comes from the battery. Then jump power from that terminal or the battery positive post, to its small terminal. You should hear a click and the other large terminal that feeds the starter should be energized. If not, then the solenoid is bad. If good, then continue tracing the power through the key switch to the battery until you find the break in the power path.   All testing can be done with a 12 volt light or a voltmeter.  Most equipment has safety switches in  the seat and on the blade engagement lever. Check them by temporarily bypassing with a small jumper wire.

Let me know how you make out.
Michael