Thursday, July 14, 2011

john deere L120 lawn mower blows 25 amp fuse

Do you have enough clearance to see underneath the mowing deck? Are the blades tangled up with each other?

if you don't press the rearward-mow button (yellow in color) before you step on the reverse pedal the blades will simply disengage. You would then have to re-engage them once you're finished backing up.

try holding the rearward mow button in when attempting to engage the blades (irregardless of the ground direction - as a matter of fact, forget attempting to move the mower, for now). Just try the button trick before you even try to mow. If this still blows the fuse, try to slightly press the foward pedal and then engage the blades. You may have a faulty PTO switch (blade engagement knob) but you may not. Whenever you have a electrical system problem, it is never simple to diagnose, especially if you have never encountered the problem before. If the PTO switch is at fault, it is part number AM131966. Check with a local John Deere dealer to order part.------------

There is a yellow button that shows a cog-like circle with a tractor behind it, and an arrow pointing backwards behind the tractor. That is the rearward mow button.
A bad switch to a pinched wire somewhere. Try to turn the blades by hand (with the engine off of course) and see if they are stuck. It will probably take some force if it has an electric PTO.

Another thing you could do Is follow the wires from the switch and look for a spot where its rubbed through the insulation and shorting out. Also you should be able to raise the deck and look under and turn the blades by hand. If you flip the switch and the engine boggs down then I would say its bound up under there.

This mower has a convenience socket (power outlet) on it. Check it for something shorting it. Should have a wire from the amp fuse running to it. If in doubt, pull off the connector from the back of the socket and see if the fuse blowing stops.

clean the dried mud and grass from all around, everywhere, underneath where the three blades are.
The blade should turn and lower a bit.If its not lowering or turning there is a problem.--------
the blades should lower when they engage.If not there is problem.-------

Also if you can find a pully with a wire going to it, that's your you electric clutch . unplug it then flip the switch and if it doesnt blow the fuse then your clutch has a problem .--------- mostly this is your problem.
need to do to take the deck off and do an every speck of everything cleaning underneath the deck.


Before you remove the mower deck check if you are able to turn the blades around by hand (without the engine running, ). If so, lets not yet remove the deck. First, lets see if you can hear the electric clutch engage. Be sure to have a new fuse in place. Sitting on the machine and having all controls in neutral and the clutch pedal depressed, turn the key to the run position (without attempting to start the engine), pull the PTO switch out and listen for a tinny sound. If unsure if you heard anything, push the PTO switch back in and then out again...listen carefully, it won't be necessarily loud. If you hear nothing then you need to determine if it is the electric clutch itself or the PTO switch or possibly something else. If you do, in fact, hear this engage AND you were able to turn the blades by hand then follow the next step. On the underside of the chassis and under the engine you will see two pulley arrangements with the bottom most being the pulley that runs the mower deck This will appear bulky as it is the electric clutch assembly. There is a wire connector in the vicinity of (and running to such) this that can be unplugged (two wires on each side of it related to such). Unplug this and check for any corrosion in the connector. If so, clean this out with electrical contact cleaner and push and pull the connector together and apart several times to help remove any excessive corrosion. Reconnect the connector and try to operate the machine again .----------------

I called the john deree tech and he confirmed the magnetic clutch issue:---
This is what he tried:---
He followed all the wires and they were fine. He checked everything, took the cover off the belts and pulleys and cleaned out all the grass and dirt. I told him I was able to turn the blades by hand, which he confirmed. He had me start the mower and looked underneath while I engaged the blades and they were barely moving so he told me to turn it off. He said the magnetic clutch was defective or faulty and it would have to be done at his repair center..