Toro Wheelhorse model 57450 electric problem

[silverstatefr]

Hi everybody,

first excuse my poor english,
My wheelhorse started perfectly, but when I engaged the clutch last saterday it was OK for 30 seconds or 1 minute. After that I lost the cutting function. The engine always ran until I stopped it. I saw that the fuse directly behind the ignition switch (main wire) was cut. I have a short circuit even in the stop position (a new fuse goes red). I do not see the relation with the clutch. Maybe it's normal. It is impossible to start now. I don't understand the function of the diodes on the electric diagram or why a 7.5A fuse on the light circuit? Could be the cause? Could someone explain to me. Or if you have an other idea to check. I checked the ignition switch but it is OK. Could the coil (magneto) be the cause?
Thank you. I appreciate a lot my tractor and would like to keep it again.
Silverstatefr

 

[Rivets]

There should be a second fuse in the wiring between the starter solenoid and the B terminal on the key switch. If this fuse is blown the unit will be completely dead.

 

[mechanic mark]

Inspect & test seat switch.

how to test seat switch on riding mower - Google Search

Remember to go "Full Throttle" before engaging PTO clutch.

Amazon.com

how to test pto switch - Google Search

 

[silverstatefr]

Thank you Rivets but what do you mean when you say "the unit will be completly dead"? On Internet I have found a possible cause with the TVS diode which are used to protect electrical system :

A transient voltage suppression (TVS) diode assembly is used to protect the electrical system components from power surges created by energizing and de-energizing the PTO clutch coil. The TVS diode plugs into the main wire
harness above the right rear corner of the operator's platform. The TVS diode can be identified by its yellow color and TVS diode symbol on the end of the diode body. If the TVS diode fails, it may cause a short in the circuit. This type of failure would cause fuse FB1–F4 to blow. Test the TVS diode if fuse FB1–F4 blows repeatedly. If the TVS diode fails, it may cause an open circuit. This type of failure could damage the TDM controller output for the PTO clutch. Test the TVS diode if the PTO clutch coil does not energize or de-energize correctly
It 's for groundmaster but it be could be similar for me. I have to find this component. I hope I can save my WH.
For Mechanic Mark, thanks too. I was on the seat when the problem arrived. I will check it before next weekend. And I was on the full Throttle position. Always.for cutting.

 

[Rivets]

If the fuse I talked about is blown, NO cranking, NO lights, NO PTO, NOTHING.

 

[StarTech]

Make sure you have turn the blade clutch switch back off and check the fuse. (Operators and techs do forget to turn the clutch off sometimes) If still blowing then you have a short in the wiring; otherwise the electric clutch is probably partially shorted and drawing more than 7.5 amps.

Your engine has a tri-circuit stator and the diodes are just rectifying the AC into a pulsing DC voltage. One diode is providing negative ground system voltage and the other is providing positive ground voltage so the second fuse is necessary to protect the stator from short circuits.

I don't see TVS diode used in this circuit schematic. I see a module that is part of the safety system. Not sure as to its actual operation. Don't know why it is there as it more like a dummy module.

 

[silverstatefr]

Thank you StarTech, it's the diagram of my mower. If a remove the wire (black) between the diode and the engine there is no short circuit. So I have to check the diode. Maybe I have a problem with the coil. I don't see why when the ignition switch is off (M &G) I can have a problem due to the clutch. I have 12V on B and this voltage goes to the diodes circuit annd to the engine. I suppose that one diode is NOK. I could check more thursday to saturday.

 

[silverstatefr]

One of the two diodes is NOK. Before changing the complete wire I want to build my own circuit to verify if only the diode is the problem. I will used 1N5404 diodes. I saw I have an alternator behind the flywheel. It's new for me. The engine is a 286707 model. If a turn the flywheel with hand I have a voltage at the output (wire coming from the engine to the diodes). Maybe the alternator is always OK. It's a bit difficult to find in France and expensive (more than 100$). For a lawn mower that have about 30 years old. I give you more informations later after testing with diodes.

 

[silverstatefr]

The diodes

 

[Rivets]

This manual might be of some help. https://www.briggsandstratton.com/c...a/en_us/Files/FAQs/alternator_replacement.pdf