Various electrical issues: Detailed chronological story inside! :-P

[s10xtremist]

A few months ago, I bought an '07 LT2500 50" with a 25HP Generac with 141 hours showing on the meter. I'm not sure, but I have reasons to doubt that this is the original hour meter. Anyway, it performed great for the first few weeks (cutting about a 1.25 acre lot once week), but then it didn't want to start the next weekend. The battery could barely turn the starter. I found the two fuses/holders by the motor to be very corroded with a white chalkiness. One was a 30A that appeared to go to the starter solenoid, the other was a 25A that appeared to be the charging wire off the regulator. The 30A wasn't blown, but was very deformed and had bubbles in the plastic as if it had gotten hot. I don't think this was from engine heat, either. The 25A had an intermittent connection due to the corrosion, so I suspect that the battery wasn't being charged as it should during mowing. I scraped and cleaned as much of the corrosion as I could, installed two new fuses, and parked the mower with a trickle charger/maintainer on it for the week. The following weekend, the mower had starting issues. I would have to hold the key to the cranking position, then move the fuse holder with the 30A fuse in it all around until I found the "sweet spot" where the starter engaged. I figured the fuse holder has a broken connection on the inside and just needs to be replaced. One or two more mowings go by with the same problems, but I haven't got the time to find new weather-resistant fuse holders, nor replace them. Time has always been scarce for me- that's why I have a mower like this for just 1.25 acres. Then, I realize another problem: I have to hold the key switch to the cranking position and move it around a bit until the starter engages. So, now I'm wigging the key switch and the fuse holder to start this thing. About the same time I realize this, I find that sometimes the starter and all is actually engaged (once I find my "sweet spots" with the fuse and key switch) but it's not turning the motor. During this, I notice the voltage on the meter is down to 7 and 8 volts, which indicates a severe drag on the battery. Speaking of, the battery wasn't very old (if not brand new) when I bought the mower- the date sticker says 4/12. I'm thinking the previous owner was having these issues and didn't know what to do. So he slapped in a new battery which would have the ampacity to hide these intermittent issues, and washed his hands of it.

So, this is where I'm at currently with this mower. I believe all these issues are related, and I'd like to get to the root problem, then work my way up from there. My hypothesis is that the starter is failing, and it intermittently puts a load on the electrical system, which burns out contacts in the key switch. The corrosion in the fuses is just from the mower being stored outside at the original owner's place. But still, these are more points of poor electrical connections that add to the problem. Between the failing starter drawing more current through the key switch and burning it's contacts, and fiddling with other poor connections on the starting and charging side of the system, the battery has been drained too much and too many times and is now permanently damaged and it no longer has the capacity to fully maintain a charge when loaded. The other side of the key switch issue is that I would think that the starter solenoid is fed through a relay, so the amperage isn't going through the key switch. Is this correct?

What do you guys think? Are there any wiring schematics for this mower available here or elsewhere online?

 

[s10xtremist]

UPDATE:
I disassembled the key switch and cleaned the contacts. One of the contacts was burned down, so I bent it up to help the connection. I have a new switch on order. I pulled the wires out of the two fuse holders and wire brushed the terminals clean, crimped down the "teeth" with needle-nosed pliers to bite the fuses better, then reassembled. I verified that all other connections were clean and solid. With the battery fully charged, I turned the key in the normal manner and the engine spun. It popped off a little as if it was going to start just as I was releasing the key. It probably would have fired and ran almost instantly if I had choked it. I turned the key a few more times and the engine spun a few of those times, and a few times the starter just clunked. I noticed the battery was rated at 180CA (145CCA). My owner's manual didn't list any battery specifics, but an online manual for a 2005 mentioned a 295CA battery. I would assume mine would be the same, so, I'm 115 cranking amps under what is spec'ed from DC. I'm getting a battery tomorrow...

 

[s10xtremist]

I guess you guys are all just as stumped as me!

Today's findings:

I replaced the battery with a 410CA unit, so lack of amps is definitely not the problem. While the battery was out, I extended some wires so that I could mount the two fuse holders to the body instead of letting them just hang out of the harness. Reconnected everything and turned the key- nothing but a solid "clunk" from the solenoid. But, it engages solidly every time, so that shows a slight bit of progress. The starter won't turn, though. I removed it from the motor and put the battery cables directly on it. The solenoid engages and the starter turns slowly. I forgot exactly which terminals I applied the positive lead, but it made the starter turn at what appeared to be full speed, but the sprocket wasn't engaged.

Do I have something wired incorrectly? I don't see how that could have happened. There are only two connections, and each of them are very different sizes.

Can I fully and accurately bench test the starter and solenoid?