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Just thought I’d share this for anyone out there who may be experiencing trouble with lawn equipment, particularly a lawn tractor having starting problems. After a long tussle with the machine, a 20 year old MTD 13 HP, I believe I’ve solved all the issues with it not turning over.
I tried new batteries, to only limited success. The starter motor was definitely bad. It took me a while to realize this though. The deterioration in performance is slow and it did not dawn on me until it still would not turn over, even with a new battery. A replacement was easy and cost about $40. One or more of the safety switches may have been faulty. I replaced both of them.
I also replaced the ignition switch and starter solenoid, neither of which were faulty, looking back now, but it eliminated them as a possible issue.
The real bugaboo in the whole system, difficult to figure out, was the fuse holder in the circuit to the starter solenoid. It had corroded over time, and the fuse made poor, intermittent contact. It either worked great, or not at all. Replacing the fuse holder along with a 20 amp fuse, a new battery, new starter motor, all new safety switches and a battery cable, must have taken care of the problems, there’s nothing more to replace.
Dealing with multiple issues is always a challenge, as quite often you don't even know that is the case. You fix one issue, as I did with the safety switch, it works better for a short time, then you go back to a problem. It gets frustrating, and I think this is where a lot of good equipment gets abandoned for a new unit. Be patient, and go through each item carefully. Once it's been replaced, consider that as a non-issue. The good thing about a lawn tractor, at least this type, is that there is a limited number of items which can go wrong. The fuse holder issue was the hardest to figure out. I had suspicions before, but it took me a while before I actually changed it.
The last thing, I believe, a person should suspect is a faulty wiring harness. It's still the original on my unit now, and it seems to function OK. I'd say that absent any obvious physical damage to the wires, I'd leave that to the very last, and even then, just look again for obvious damage and replace the faulty wire.
The only other possibility is evil spirits, which I’m not qualified to deal with ??. All you mechanically inclined types have a good day, and a good laugh.
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Sorry to see as a "The Maintenance Guy" you didn't (from what I'm reading) first off didn't have a wiring diagram.
From there you could have followed the current path from battery to all components.
You did the "what if" repair.
Like too many people just keep spending money on parts not needed.
Glad you finally found your problem.
But the question is ? How did that fuse holder melt ?

Fuse holders get cooked all the time. Just a little bit of moisture is all it takes for corrosion to start and make a high resistance connection which generates heat. You should work on boats exposed to saltwater. I have seen fuse panels that would make you cry.

Hammermechanicman said:

Fuse holders get cooked all the time. Just a little bit of moisture is all it takes for corrosion to start and make a high resistance connection which generates heat. You should work on boats exposed to saltwater. I have seen fuse panels that would make you cry.

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Fuse holders in boats maybe in a saltwater atmosphere. But on a lawn mower ?
I'll just say the fuse holder had a poor loose connection to cause the heat to melt the holder.
And if it was on the positive feed wire from the battery never blew the fuse.

I have replaced plenty of fuse holders on mowers.

Hammermechanicman said:

I have replaced plenty of fuse holders on mowers.

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Did one yesterday due to wire corroding off where it connects to the battery wire connected at the starter solenoid,

ILENGINE said:

Did one yesterday due to wire corroding off where it connects to the battery wire connected at the starter solenoid,

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And what caused the wire to corrode ?
Or did it break because it wasn't tied up in the harness correctly causing it to just flop around ?

The wire got a case of the green crusties. Could of been some battery acid contamination migrating down the wire from the battery or could be due to the fact the mower sets out in the weather. Wire broke right at the crimped connector

The fuse holder was parachute connected to the frame so not much chance of flop around. One of the connectors inside of the fuse holder also separated.

Your reasoning is a possibility.
I have seen moisture migrate in a wire before.
But if it did wouldn't you see the positive cable from the battery bad also ?
The positive cable goes straight to one lug on the solenoid where the fuse wire gets it's current from.
How did the corrosion migrate ?

The corrosion migrates down inside the insulation on the wire. But could be just water running down the outside of the battery wire and then pooling on the crimp connector.There was some corrosion on both ends of the + battery wire but not something that is currently causing issues. A 6 gauge battery wire can handle corrosion better than the 16 gauge fuse wire. In this case the rest of the mower will be junk before the corrosion on the battery wire causes major issues.

OK thanks for that info.

Richie F said:

Your reasoning is a possibility.
I have seen moisture migrate in a wire before.
But if it did wouldn't you see the positive cable from the battery bad also ?
The positive cable goes straight to one lug on the solenoid where the fuse wire gets it's current from.
How did the corrosion migrate ?

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Corrosion is a GALVANIC reaction between 2 different metals in the presence of an electrolyte, usually water
The reason why you see a lot at the battery - and very little at the battery + is because the flow of electricity at the - strengthens the reaction & at the + it reverses the reaction
When this was noticed it begot a whole field of engineering called CATHODIC PROTECTION where things exposed to the elements were perminantly energised to drive the galvanic cells backwards .
IT is the reason why a lot of motor vehicles went from - ground to + ground in the 40's to prevent all of the ground connections from corroding .
It was not particularly successful so in the 70's most vehicles reverted to - ground.

All corrosion is galvanic in nature be it macro , 2 or more different metals in contact or micro differences in the electro potential within the actual metal grains themselves.
Any 2 metals and in many cases a metal & a conductive non metal can make a battery remember the potato batteries you should have made in high school chemistry / physics ?
For simplicity we give specific classes of redox reactions specific names.
If we pull the surplus electrons out of the reaction vessel we call it a battery
If it happens to metal stuff we have made we call it corrosion
They are all the same thing.

Richie F said:

Sorry to see as a "The Maintenance Guy" you didn't (from what I'm reading) first off didn't have a wiring diagram.
From there you could have followed the current path from battery to all components.
You did the "what if" repair.
Like too many people just keep spending money on parts not needed.
Glad you finally found your problem.
But the question is ? How did that fuse holder melt ?

Click to expand...

Just plain old corrosion, nothing melted. The connection was intermittent, and in addition the starter was bad. Makes it tough when a couple things wear out at once.