Snapper not charging battery

Snapper Hi-Vac 28" with 10-hp Briggs & Stratton
Electric Start, about 3 years old.
Will start and run great with a fully charged battery, however will not keep battery charged. Tried two known good batteries. Battery voltage checks about 12.4 volts, wheather engine is running or not. Increasing throttle has no effect on voltage. After several starts of course there is not enough voltage to turn over the engine. Postive battery cable connects to what I think is the solenoid, which I think has nothing to do with the charging system. The in-line fuse to this is good. I'm thinking it is the alternator or the voltage regulator. If this is the problem, where are they located and how do I replace? Thanks.

 

The alternator is under the flywheel, this could be bad, or the diode.

 

There should be a red wire coming out from under the engine shroud near the starter, possibly with a white wire next to it. This red wire should be connected to either the positive post on the battery or the battery post on the solenoid, and sometimes they run tto the battery post on the ignition switch. Either way, connect it to the battery. If it is already, remove it and check for voltage on that wire with engine running. If none, check voltage in AC mode. If you see significant voltage there, the diode is probably bad.

 

Thanks Guys,
I did just what cheese said, last night. I get no DC voltage at the diode, but do get AC. The diode appears to be shorted. I will replace and get back to you.

 

Have you unplugged the seat safety switch? Some lawn mower manufactures make it so the battery does not charge if you unplug the seat safety switch.

 

I didn't mention it in the first reply, but did you have to test above the diode to get a reading in AC mode? If not, and you got a reading after the diode, you may have a bad charging stator as well. This would mean the diode shorted instead of opened, and that would allow battery voltage to short straight to ground through the windings of the charging stator which normally burns them up. A diode is cheap enough though...give it a shot.

 

Thanks Guys for all your help. I have one more issue.
The bad diode is a straight short. Chesse seems to be correct that it has burned up the stator. I replaced a new diode and still get no DC,(I said earlier that I have AC, but it is very small 0.4vac) however I seem to have a duel stator circuit. There are two wires coming from under the houseing to a two pin connector. The connector that plugs into this and goes to the solenoid (and on to the positive term. battery) only has one lead. Apparently the other curcuit is for lights.(this mower has no lights). I get DC throught the diode when I hook it up to this lead. The battery is about 12.4v without engine running, but goes to about 12.9v when it's running hook up this way. My question: Is there anything wrong with just using the other half of a duel stator circuit ? Kind of like going to the backup without having to replace the entire stator.

 

I don't see why not, as long as the diode is in place correctly.

The only thing I can think of that could cause a slight problem is that the amperage created by this secondary set of windings is much lower than the amperage of the charging set of windings. This will mean it will take the engine longer to charge the battery. On a snapper, with no lights, no electric pto, or anything like that, I would think it would maintain a charge nicely in the amount of time it takes to mow a small yard.

 

Seems to be charging battery just fine. Thanks for all the help.

 

Glad it's working! Thanks for the update.