Blowing fuse on Craftsman riding mower after startup

[jaxs]

@jaxs In this case the seat switch is not part of the start circuit, so doesn't effect starting. Shorted voltage regulator normally blows the fuse as soon as the key is turn on. A short in the wiring could also cause the regulator to put out more amps than the system can handle and blow fuses, but not likely. In this case the voltage regulator would be connected to the key switch since it also involves an amp gauge. The issue could also be heat related meaning that the failed component only shorts when hot. Electric PTO clutches will do that as well as the regulator and fuel solenoid if equipped.

Thank you for sharing that. To be certain I'm clear on seat switch,does "In this case the seat switch is not part of the start circuit, so doesn't effect starting" mean one can stand beside machine,push clutch down and start machine while seat is vacant ? What is the seat switches purpose?

 

[tomplum]

The majority of riders are this way. Many Kubotas as an example are not as an example. Seat switches are in the run circuit so that should the operator leave the seat in a potential travel mode it kills the engine. My head is recovering from a bug here and I haven't even tried to wrap my head around the schematic. A gidgie operator presents relay can cause at least some of the issues. Any old headlight relay can do. Voltage regulators on these can be suspect, can sometimes put out higher than the 15 AMP rating. I've seen them go 17/ 18. Be sure that there is a ground strap on the VR mounting screws. I think that I recall something about the headlights not working. Husqvarna has a weird habit of combining the safety switch ground with the headlight harness- before the connector of course. Have had at least a handful of customer units for a no crank that had a bunch of parts tossed on it, only to have found that the harness repair by the customer didn't tie the 2 ground wires together. And while the tank was out did you note a ground harness there and service that? Think of these tractors having a chassis ground to support the main components and the separate safety line ground as you wander through this.

 

[RandyT]

@tomplum The early MTD mowers with the mower in reverse turn the key and push the button systems were wired through the headlight circuit. So if the headlights burned out or the customer disconnected the headlights the mow in reverse feature wouldn't work.

And the two mowers that I have personal experience with having to be on the seat to start the mower is Kubota and Scag.

@jaxs Your description of the seat switch starting is correct. the purpose of the seat switch is to shut the mower down in case you leave the seat without turning off the deck and setting the parking brake. Or to kill the mower if you fall off of the seat. It grounds the ignition module just like turning off the key.

 

[rangerfredbob]

This is from '96, it's simpler than newer stuff. The fuel tank is in the rear under the back fender, there is absolutely no wiring near it other than the 2 wires to the seat switch which run by themselves ziptied to the fuel line for almost 3'.

There is a ground wire to the engine from the voltage regulator, if it isn't a billion degrees tomorrow (supposed to be like 99) I'll clean that off and reseat the regulator connector, can't hurt...

I'll look into the headlight circuit, see if the bulbs have just burnt out over the last two years or missing a ground, that would be silly...

Haven't looked through the diagram yet, too hot in the house by the computer... I'll try to print that part out at work to make it easier...

It's a simple system, it shouldn't be this odd . I'll have to admit it's been a while since I wrapped my mind around the odd ignition switches on mowers and the reverse polish wiring of the relay... I know they make it confusing so the average Joe doesn't bypass it all but come on .

I don't like throwing parts at it, but it needed the PTO switch anyway before the knob fell off, and a seat switch is $8, so with the 140 piece fuse kit I'm in it like $40... that's what, 20 minutes of shop labor if I took it somewhere?

Thanks for the help, I'll keep you updated tomorrow hopefully...

 

[Fuddy1952]

What would be good is instead of 30A fuse is wire a 30A circuit breaker in series with an ammeter. A short would trip breaker, ammeter would show current draw while you try different things.

 

[rangerfredbob]

Unless the seat switch was somehow shorting to ground I have no idea... I got the new seat switch tonight and put it in and it worked just like normal... Seeing as though the seat switch gets key on power and powers the relay that's the only thing that makes sense?

I mowed for like an hour after it started working, clutch in and out, shifting between high and low, forward and reverse...

 

[CobyRupert]

 

[rangerfredbob]

Just to follow up in case someone else finds any of this nonsense useful...

I have no idea what was going on originally but it still working perfectly... must have been the seat switch somehow? The mower hasn't missed a lick, but being hot I haven't mowed a whole lot with no grass growing... we'll see this fall since it's started growing again...