OK, think about this. Your fuse blows while you are trying to put it in? And you don't even have the ignition switch turned on? Right? If this is true, your short is going to be in the wiring between the the fuse holder and the ignition switch. The ignition switch itself might be defective. If you can access the back of the ignition switch, disconnect the wire harness from the switch and try a fuse with the switch out of the circuit. If removing the switch wiring connector stops the fuse from "blowing", you probably have a short to ground inside the ignition switch. If the fuse continues to blow even after unplugging the ignition switch, you likely have a shorted wire. In that case, you need to search for physical damage to the wiring harness that connects to the ignition switch. Look for chafing, crushed, or if the wiring harness "bends around or over" a sharp edged metal surface.
If you were trying to replace the fuse while the ignition switch was in the run position, and does not blow when the ignition switch is turned off, the short is somewhere on the "fed out" side of the ignition switch (and may be a real bear to locate).

Thank you for the information. I will check the ignition switch later today once I can get out and buy some more 20 A fuses...I went through them all yesterday.

You are correct that the fuse blows with the ignition switch off and no key in it.

I will let you know how it goes later today.

Thank you so much for your time.

You have a direct short to ground,a wire must have rubbed something metal to cause this .....now you have to find the wire .....if the fuse didn't blow,you'd be able to find the wire by following the smoke !!! Jim

***"if the fuse didn't blow,you'd be able to find the wire by following the smoke"***
100% true! I now feel I should add that fuses should replaced with a fuse of IDENTICAL AMP RATING ONLY. As Jim mentioned, SMOKE!!! Putting in a "substitute" fuse of a higher AMP capacity, can cause damage to the vehicle wiring that hard to imagine. We (old mechanics) used to "humorously" tell the "young 'uns" coming into the trade that all the components in a vehicle electrical system, were filled with "pressurized smoke" (except for the battery, which was filled with "pressurized acid", but that's another story). Anyhow, we would tell them that the smoke, was held inside the "copper", which carried the "juice" everywhere. The culmination of the "leg pulling" yarn was the "solemn" statement: "You have to be careful working on electrical systems! If you ever screw up and "let the smoke out", it'll never work again."

Thanks for all your help guys.

I bought some more fuses...pulled the harness for the ignition switch and the fuse still blew. So I went over every wire I could looking for a fray. Well I found a wire that was frayed...basically missing about 3 inches of plastic. It was the wire that went from the fuse box across the engine to the other side. It was laying on the engine and there was my direct short to ground.

I appreciate all the help. You guys saved me hundreds of dollars for something so simple.

You are welcome, glad to help, neighbor. That is what this forum is about. Neighbor helping neighbor. I hope you wrapped that wire really well so it won't be "afraid" any longer. :^)

Missing 3 inches of insulation on the wire? wow...

Was it near the exhaust system that so much was missing - or perhaps cracked or rubbed off ?

It may be worth trying to tie wrap that section of wire someplace secure. Even if you have to splice in a longer piece (make sure its the correct gauge of course - or you could see a LOT of smoke!).

njdpo... I did end up splicing in a new wire (slightly large gauge) because there was so much missing. It doesnt seem to be a really really hot spot in the engine nor does it seem to be in a place where it would rub excessively. Its no where near the exhaust. Its a wire that comes across the back of the engine.

I will keep an eye on it to see if there is any further damage to the new wire. If so I will reroute it to be safe.

I can tell you this: It doesn't really need to "rub", in the sense of moving across the surface in a back and forth motion or movement!!! All that is needed is for the wire to "touch" or press against certain components that produce "harmonic vibrations" (engines do this) and the vibrations themselves provide the chafing action that can erode wires, hoses, cables and just about anything that touches, but isn't secured to, the vibrating component. If possible, "tie wrap" or "zip tie" the wires away from contacting the engine surfaces. If you can't effectively get the wires off of the engine (because there is nothing to anchor to??) at least attempt to put some type of protective cover around the wires. a short length of automotive heater hose (of appropriate inside diameter) can make an effective protective cover. Use only enough of the hose to extend about one inch beyond the ends of the damaged section of wiring (so in this particular case, five inches of hose). Slit the hose from end to end (careful with that knife Eugene). Carefully push the slit hose over the wire harness. After the hose is in place over the harness, rotate the hose so that the slit is opposite the point of contact with the vibrating component. I recommend using silicone RTV sealant to fill the inside of the hose. Use the screw-on nozzle that comes with the RTV tube and press the nozzle into the slit. Work your way along the slit as you squeeze the RTV into the hose. The RTV will adhere to the hose and assume the shape of the harness, effectively shielding against vibration chafing. This will provide a lifetime repair. If it's only a single wire (instead of a harness) you can use fuel hose or vacuum hose for the over wrap. But also, if it's a "single wire" you can just splice in enough extra wire to route it through a safe passage.

I'm having similar problem. Found the short in the plug under the mower that plugs into the PTO clutch. I tried to fix it and but think it shorted out. Now I have no electrical power either, and the fuse doesn't look blown? Any help would be great.

If there is an actual short, my guess that it is the clutch itself. But if there was a short, the fuse then should be blown. Best start a new thread and tell us what you know so far...

Ok here it goes. My l120 has or had a pto clutch problem. I burned up 2 switches so far. I jumped out the clutch, and it runs. Not believing I needed a clutch, I installed a switch separate from the factory PTO switch. Started the tractor and it worked good for 4-5 minutes. Then the tractor died. Now the main 20amp fuse has blown. Have not touched it since that happened. Guys need a little help if anyone could share there experience. Thanks for listening.

dostle - first off, best off for you to start a new thread - this one is getting old and multi-threaded.
2 switches and then a 20a main fuse blown indicates an excessive current draw someplace and the best suspect in your case is the pto clutch itself (shorted windings). Such can be tested by use of a VOM meter. Specs for such can be gotten from the pto mfgr's website.

Thanks Rex. I found it,, and have ordered a new clutch. It finally failed completely. Appreciate the response.

anyone have a solution for no power at the pto connection. Checked all the lines for break and contiuity, seat switch seems ok as does the reverse safety switch.

using a VOM or a continuity tester, you'll need to trace current path at least from ign sw thru pto sw on thru safety sw/relays down to pto itself incrementally to isolate problem... or take to shop.

Does anyone out there have a John Deere L120 have a issue with the following it has a extra regulator box on side to keep battery charged while the electric PTO is working also need to know or would like a pic of how it is wired it shows voltage on the regulator when switch is off if anyone can help with pic of how theiers is wired or info would be greatly appreciative.

i have same type problem as some other people. i have a john deere 420 lawn garden. when i turn the pto switch on my battery light comes on. i can mow about 20 minutes then it blows the fuse. do you think it is the pto coil?

A 420 isn't even close to an L120. Please start a new thread. It could be a coil. I'd start adjusting the end gap first if it were my money.

Ok so I have a john deere l120 I have changed cynoid , spark box , both coils ,ignition switch,relay, fuse , clutch , clutch wire harness, found wire going to coils burnt. But my mower will only just tune over wont actually start . I frustrated and have been at it for over 3 months now . Help before I get the gas can and a match

You should really start a new thread instead of adding to a thread about an entirely different problem + the other people that did the same.

Have you checked for spark?

With a burnt wire going to the ignition module, it may have blown the module if 12V was shorted to it. It shouldn't have voltage ever. It is grounded to kill spark.

I did

looking for help with a L120 blowing the fuse . changed the ignition switch, traced the red wire from the fuse to the engine. All is good with that. How can you tell if the solenoid is bad?