Why would a mower melt 20 amp fuses?

[cwbyeng1300]

I had a welder with an ONAN engine. It started burning out batteries. Found a bad voltage regulator. Engine was making 18 volts & overcharging the battery. Simple to test for - check battery voltage while it is running.

 

[twowoode]

I had the same issue recently with a Koehler 26 hp . I got it from a friend of mine that thought he had blown the engine. Traced it to the new electric fuel shut off he had installed. It was pulling a very high resistance. So my educated guess is something is pulling a high load. I think you found it when you said it only happens when you engage the blades. You only have the switch and engagement clutch to test

 

[EddieWalker]

I replaced the PTO Clutch this morning and I cut off the holder for the fuse and installed a new one. The wire to the fuse became too hot to touch after a couple minutes of just starting it up. I never turned on the PTO, I just started it and held the wire to see if it would get hot. It got VERY HOT!!!

 

[jaxs]

I replaced the PTO Clutch this morning and I cut off the holder for the fuse and installed a new one. The wire to the fuse became too hot to touch after a couple minutes of just starting it up. I never turned on the PTO, I just started it and held the wire to see if it would get hot. It got VERY HOT!!!

Ahh-haa,we now have something to work with. "IF" from the point where wire overheated,the wire "ONLY" leads to and serves clutch,there is a high resistance short circuit. "DEAD shorts" aka low resistance shorts blow fuses. "HIGH RESISTANCE shorts" heat up and melt other components in addition to fuses. It might be wise replacing fuse with a SMALL 12 volt bulb (tail lamp,dash light) while looking for the short. The bulb will limit amp draw on wire to amp capacity of bulb which isn't enough to damage wire. The bulb will glow until short is corrected which point bulb will stop glowing.

 

[jaxs]

I think you may have covered this earlier but it is worth double checking. If clutch only has 2 wires,make certain which is + and which is -. Not likly but possibly fuse can be in - wire. I mention this because if fuse is in + wire,the switch is probably in - wire.

 

[Midniteoyl]

PTO Clutch coil going out?

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[lpakiz]

I second the suggestion to use a light bulb in place of a fuse (temporarily) to find a short. However, I used to use an old sealed-beam headlamp. These pass around 5 amps, which is not enough current to damage any components. An added benefit, as noted, is that when the short is active, the bulb glows brightly but when the short is removed, the bulb will revert, depending on load, from dark to orange glow.

 

[KWentling]

I agree with the guys recommending using a test light to replace the fuse. I looked a little for a wiring diagram for this and all I found were some pretty poor ones. It did look like there could be other components down stream of the fuses besides the clutch. A good schematic would help a lot.

 

[lpakiz]

If you're using a small test light for a fuse, be aware that any small, legitimate load will cause the bulb to glow brightly. With a "bigger" fuse, like a seal beam headlight, it takes more current to make it glow.

 

[CaptFerd]

Buy the time your at page 15 of this post you be at a very expensive bunch of pot shots of everyone's suggestions. You need to learn this electric system with a schematic and start trouble shooting all your switches, relays and wires in the ptos circuit. The pto is fed directly from battery voltage. I would start with the pto and ignition switch. Your getting a short from the battery to ground through this circuit from somewhere definitely.