John Deere L100 won't crank

mamick122July 27, 2014

I have a 10 year JD L100 with the 17.5hp B&S motor. Yesterday I shut it off and now I cannot get it to crank. Here is what I have tested:

- Tested all three safety switches (seat, PTO, and brake) all function correctly according to ohm meter.
- If I jump 12 volts to solenoid (Disconnect hot wire form ignition) it cranks, but does not start with key on.
- I then disconnected connector from back of ignition switch and put a jumper between Battery "B" and Magneto "M" and put 12 volts directly to solenoid, again cranked but would not start.
- With the ignition switch disconnected I tried to jump Battery "B" to starter/Solenoid "S" on the connector and it does not attempt to crank.
- Also the lights do not come on when the key is in the light position, if I jump 12 volts to the lights directly they work
- I connected the ignition connector back to the ignition switch and measured the voltage between the lights "L" and ground and it shows less than one volt when the switch is set to the Lights position.

I don't think it is the ignition switch since when I tried to jump around it through the connector it didn't work either.

At this point I am guessing a short somewhere. I am at a loss trying to find the short, is there anything I am missing?

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Well, when you connect B to M, you probably fried the magnetron.
That wire is GROUNDED to KILL spark. Otherwise, it works just like the coil on your batteryless walk behind mower.

Did you think to check the fuse?

    Bookmark   July 27, 2014 at 8:09PM
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Yes, checked the fuse, I even measured with ohm meter to make sure. I also tried connecting B to L directly and the lights won't come on. But if I connect the battery directly to the lights they do come on.

    Bookmark   July 28, 2014 at 7:02AM
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Do you have 12V at B on the plug?

    Bookmark   July 28, 2014 at 9:53AM
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Was traveling for work just got back and checked yes, there is 12V on B.

This post was edited by mamick122 on Thu, Jul 31, 14 at 22:58

    Bookmark   July 31, 2014 at 10:35PM
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You hav 12V at B.
You connect B to L and have no lights?
Doesn't make sense.

    Bookmark   July 31, 2014 at 11:00PM
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OK- Looking at the schematic-
The L terminal is connected to the B terminal at the Voltage Regulator. RED & PURPLE.
At the harness connector-

The actual "feed to the lights is A2.
Kind of backwards from "typical" schematics.
So, if you connect either B or L to A2, you should have lights.

For the crank circuit-
Key switch S terminal (purple) goes to the PTO switch.
PTO switch to Brake switch (purple/white) to solenoid terminal (purple)

This post was edited by bill_kapaun on Fri, Aug 1, 14 at 11:35

    Bookmark   August 1, 2014 at 11:25AM
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Thanks everyone for your help, I figured it out. As I looked at the battery voltage I noticed at the battery it was 12 volts but at the harness to the switch it was 11.9. So I started walking back from the battery to the harness tying to jump over to the solenoid.

When I tried to to crank from the hot side of the fuse it would not crank. I popped open the connector on the small hot wire between the fuse and the solenoid and it had corrosion in there. I cleaned it out, sprayed a little DW40 on it, snapped it back together and now it cranks right up!

Still no lights but those haven't worked in a while, maybe corrosion somewhere else. But at least now I can mow!

    Bookmark   August 1, 2014 at 4:27PM
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gotta ask - has someone been using either a power washer or garden hose to wash the machine down? if so, that may by the source of the corrosion you found... allus best to use compressed air or leaf blower to get trash/clippings off machine after each use; L&G powered eqpt isn't designed/built to withstand getting wet a lot..particularly the electrical systems.

    Bookmark   August 1, 2014 at 11:21PM
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