Craftsman won't crank after mowing lawn

[the.doc]

All the model numbers are in the pdf. I keep this mower on a Battery Minder when I'm not using it. The first time I ran it this year, it cranked ok and I mowed for about an hour and stopped it to blow the clippings off the deck. Then it wouldn't crank; not even a click from the solenoid. I pushed it into the garage and hooked the Battery Minder back to it. Yesterday was the same except that I got more than a solenoid click after cleaning it; sounded like the starter motor engaged but didn't turn the engine. Before cutting it off, I turned on the headlights thinking that would tell me whether the alternator is working; no light. On the other hand, the battery is dated May 2018.

I have no idea where the alternator is or even what it looks like. Can you guys give me some advice on how to check whether the alternator has given up or whether it's the battery.

Before starting yesterday the battery measured about 13.6. After cleaning the deck, it was about 1 volt less but wouldn't crank the engine.

Thanks

 

[Bertrrr]

I doubt you have an alternator as such , you most likely have a magneto / rectifier with voltage regulator,
If you have 12 volts and no action from the battery it's going to be a safety holding you out or a bad connection
Jump across the two big terminals on your solenoid and if it responds by turning over , either you have a bad solenoid or a bad connection . The smaller terminal on your solenoid should read 12 volts when the starter switch is engaged , if not you may have a bad switch

 

[the.doc]

Thanks, Bert. Battery Minder is a charger that at least claims to switch over to "microsecond-pulse mode" once the battery is fully charged. I leave it hooked up to the mower whenever it's not in use.

The wiring diagram in the book that came with it calls it an alternator, and I don't know any better, so I just followed that. I can't see it being the switch or the solenoid or a connection since it cranks after I've had the battery on the Minder for a while. It looks to me like either the magneto isn't putting out or the battery will no longer take a charge from that source. The manual does state that the alternator is not a very robust charging device and recommends putting the battery on a charger from time to time.

I'm really hoping that it's the battery since I know how to deal with that. If it's the magneto, I'm in trouble. I'm here looking for advice on how to figure out which it is. I thought that turning on the lights would tell me, but they work off a different winding. I think I'll try putting a voltmeter across the battery while the engine is running. How about cranking it, shutting it down immediately, and then trying to crank it again? If it won't crank, I think that would point to the battery. We'll see.

 

[Bertrrr]

Not sure how old your battery is but they're not good for more than 2 season at best in my opinion.
The magneto / rectifier rarely go bad but it's possible..
If you put a volt meter on the battery will the machine running near full throttle ,it should read 14 volts or better,
A true alternator would be belt driven , pics would help too if you post a few

 

[StarTech]

I doubt you have an alternator as such , you most likely have a magneto / rectifier with voltage regulator,
If you have 12 volts and no action from the battery it's going to be a safety holding you out or a bad connection
Jump across the two big terminals on your solenoid and if it responds by turning over , either you have a bad solenoid or a bad connection . The smaller terminal on your solenoid should read 12 volts when the starter switch is engaged , if not you may have a bad switch

Most small engines that has an electric starter do have an alternator separated into two parts. A stator and a set of flywheel magnets. Most DIYer over look the flywheel magnets that drives the stator voltage.

When these two elements combine they become an alternator when the engine is running.

 

[the.doc]

Most small engines that has an electric starter do have an alternator separated into two parts. A stator and a set of flywheel magnets. Most DIYer over look the flywheel magnets that drives the stator voltage.
View attachment 68373
When these two elements combine they become an alternator when the engine is running.

That's why I'm hoping that it's the battery; don't want to have to pull the flywheel. BTW, the battery's dated May 2018; maybe the Minder deserves some credit for that. The battery that came with the mower when I bought it failed while it was still under warranty. That's when I bought my first Minder.

I'll follow Bert's tip to look for 14 volts on the battery with the engine running. Thanks

 

[Cusser]

Attach 0-20 VDC voltmeter across the battery terminals. Start the engine. Voltage should read about 13.5 to 14.5 volts with engine running if charging system is OK; this is a test we do on automotive charging systems.