Why would a mower melt 20 amp fuses?

[5030]

Never seen an electric PTO clutch that wasn't expensive....lol

 

[90cummins]

Check for tight connections. Loose connections cause heat like you are experiencing.
90cummins

 

[jaxs]

Hot as it is in Texas these days you are lucky the tires aren't melting to.

 

[ROUSTABOUT]

Bad connections cause heat. Heat causes things to melt.

 

[jaxs]

Unplug the pto clutch and check the ohms of resistance on the clutch. Should be in the area of 2.5-3.5 ohms. There should be continuity between the two wires coming from the stator under the flywheel. There should be no continuity between either stator wire and the engine or the mower frame. Continuity to ground would indicate a shorted flywheel stator.

Also need to make sure that the contact terminals in the fuse holder are not corroded. Resistance at the fuse holder would cause the fuse to melt.

^THAT^ is most likely the problem and first thing you should test and correct before chasing any rabbits. Short , defective clutch or other excessive amp draw will simply blow fuses without overheating plastic case. If you ascertain fuse holder is in good condition (I wager 2 to 1 it isn't),post back and we can talk about tests for a couple of less likely possibilities.

 

[RandyT]

^THAT^ is most likely the problem and first thing you should test and correct before chasing any rabbits. Short , defective clutch or other excessive amp draw will simply blow fuses without overheating plastic case. If you ascertain fuse holder is in good condition (I wager 2 to 1 it isn't),post back and we can talk about tests for a couple of less likely possibilities.

Most of the time yes. Had A Kubota a few years back in the shop that the clutch was drawing 12 amps on a 15 amp fuse. the fuse is designed to protect 15 amps but don't normally carry that amount of current for any length of time and in my case it melted the plastic on the fuse, and also deformed the 8 terminal plug on the back of the pto switch.

 

[rv7charlie]

A properly sized (fuse rating) fuse will open due to overload *long* before the plastic would have a chance to melt. Assuming that is the correct size fuse, melted plastic is a pretty solid indication that you have a heat problem; not a current problem. As someone else mentioned, poor electrical connections near the fuse can cause greatly increased heat. It can be the joint at the wire-end, on either side of the fuse, or it can be the little spring-clips in the fuse holder itself. And all the above assumes that the fuse isn't adjacent to something like the exhaust manifold. ;-)

 

[MountainBuck]

I agree with KWentling and Roustabout and rv7charlie. As long as the circuit is still in the proper voltage range, that fuse should open way before it melts if the amperage is exceeded.

However corrosion in the fusebox that holds that blade fuse would cause that kind of heat.

You may be able to inspect it and clean it with spray electrical contact cleaner and possibly sand paper. They make contact burnishing tools, but I might try cutting a similar thickness feeler gauge down and taping or gluing sandpaper to it.

Disconnect the battery before doing anything and make sure the cleaner has dried (evaporated) before reconnecting.

The connectors that push up against the blade fuse might be damaged or twisted as well, perhaps not putting proper tension against the blades of the fuse.

 

[Tony H]

I have a Scag Wildcat zero turn with a Kawasaki liquid cooled 26hp engine. All of the wiring diagrams for it leave the engine out. I can't even find anything that says what start is has.

One of the odd things is that since this started happening, the water temperature gauge isn't working. For some reason, I think this is important.

I can mow for an hour, two hours, and one day, 3 full hours, without issue. But I have more days where I can only go for 20 minutes and the fuse melts. It doesn't just blow, the plastic around the fuse melts. The wires going to it are super hot!!!!! I've replaced the fuse and mowed for another half hour, ten minutes or a full hour, before it happens again. I've had days where I've replaced 4 fuses to finish mowing. But now it's getting worse. A lot worse!!!!

I traced every wire looking for a wear spot that might indicate a short. I've done this 5 different times and haven't found anything. Sometimes after doing this I can mow for hours. Today it was ten minutes and this is what the fuse looks like.

View attachment 751538

I'm starting to think that it's not a short, or a wire with a bare spot that's touching the frame somewhere. I'm starting to think that there is too much electricity going through the wires. My only guess is that my PTO Generator is overcharging and putting out more then 12 volts or more then 20 amps. The only time this happens is when the PTO is engaged and I'm cutting grass. I'm not comfortable putting a volt meter on it with the PTO engaged, but that might be my only option. I'll just have to be careful.

Something else that I noticed was that when I put my meter one of the two wires coming off of the PTO Generator, and tested for continuity to the frame and the engine, I didn't get anything. But when I put the meter on both wires, I did get continuity. Should that happen?

Is there something that I'm missing?

What else could cause this?

Is there a way to adjust the voltage coming from the PTO Generator?


View attachment 751538


Thank you

Sounds like a mouse chewed wire that sometimes shorts to Ground.

 

[Bentrim]

Ain't gonna beat a dead horse, but your problem is caused by poor connections between the fuse and the fuseholder connections due to corrosion. You either need to clean the contacts or replace the fuseholder. Then before inserting a new fuse put some electrical grease on the fuse and in the holder.