Small Engines (Lawn Mowers, etc.): John Deere mower not cranking, electric clutch, repair person

Question
I have a John Deere L110 that I purchased about 4 years ago. Over the past few years I would have a problem with the battery losing charge and finally not being able to crank the mower. I have bought new batteries and that worked for awhile and then it would lose its charge. This past fall I took it to our local small engine repair person and they could find nothing wrong other than I needed a new battery. I bought the battery and the same thing happened again. I can jump the mower off and it will run fine but as soon as I shut it off it won't crank again. What is the problem here?

Answer
The charging system may not be charging the battery or there may be a component that is draining the battery.  You will need a multimeter to troubleshoot electrical problems.

TIP:  Dis-connect and clean the battery posts and cable ends with a wirebrush.  I've fixed a lot of charging and starting problems just by cleaning the connections.

If you have a Briggs engine you need to identify your alternator.  This link will help determine which one you have.

http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_id_a.pdf

The link below will tell you how to check the charging system.  While most folks do not have a DC shunt you can still check the output voltage of the charging system.

http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_replacement.pdf


http://engines.myfaqcenter.com/Resources/BriggsFAQs/shared/pics/Faqs/105-AC_DC_t...

You can also check the DC voltage at the battery with the engine running at full speed.  You should have at least 12.5 volts DC.  If you have an electric clutch make sure it is on when you check the voltage.

Let me know what you find.
Eric