Small Engines (Lawn Mowers, etc.): Onan engine lack of charge, toro dealer, toro wheelhorse

Question
First off, thank you for your time. I have a Toro/Wheelhorse tractor Model # 32120501 with an Onan engine model#E125V-N/10964A that has not been charging my battery at all this mowing season. I replaced the battery in May and again in June thinking I bought a defective battery. The tractor was purchased new in 1992 and has been a good one. When the tractor is running it shows 12 volts on the voltage meter but drops to 9-10 volts when I switch the PTO or the headlights on. It has been mentioned to me that the voltage regulator or possibly the stator under the flywheel could be causing this condition. Is this a likely cause of the problem that I am experiencing ? The tractor is in great shape and I would like to keep it going if possible. I hope that you may have some answers and again Thank you for your time.

Answer
I don't know exactly how your tractor is equipped, but my assumption would be the voltage regulator is at fault.  I don't have an Onan book that details what the stator output is and where in the system the rectifier is.  I think the rectifier is part of the regulator on yours, but I just don't know offhand.  What you would want to find out is do you have DC voltage after the rectifier.  You would need to know what the AC output of the stator is supposed to be.  With these two values, you should be able to see if it's the regulator, the rectifier or the stator.

Little things you can do first is to re-do all grounds and battery cables.  Check the voltage at the battery with a handheld voltmeter.  With the key off the battery should show 12 or so volts.  With the engine running at operating speed, there should be a 1-2 volt jump.  If no jump, no charge.

I would recommend watching eBay for an engine service manual for your engine.  Then you would have a listing of the available stators and systems.  A Wheelhorse manual would be handy too, I believe you can get even older model ones from your Toro dealer.  Or, you should be able to get one from, https://lookup3.toro.com/request/request.cfm

Usually these will have wiring diagrams for the tractor, but I don't know about your particular one.  Thanks, PK.