Hello Guys, Need some help. I've got a Scag STC48 V 24BS mower. The key switch is new, the battery good (12.7v). When I turn the key to start, the flywheel barely turns and there is a lot of clicking from the starter. When I send 12v from the battery to the starter solenoid post (where the wire from the key switch goes), the starter turns the flywheel very well without any clicking. This leads me to believe that the starter solenoid and starter are fine but that there is some blockage in the flow of electricity from the key switch to the starter solenoid. Any thoughts, much appreciated.
To me your symptoms lead me to be looking at a bad battery. Next time you try to start the unit have your volt meter attached to the battery and watch the voltage while cranking. If it falls below 10 VDC this would indicate a bad battery cell and the battery needs replacing.
New battery fully charged. No voltage drop and the engine cranks well when a jumper from the + battery terminal goes to the solenoid green/ white post. Could this problem be the starter relay?
Just a diyer myself but have an automotive repair background, maybe you should be checking the switch battery feed wire, if you leave the switch out of the picture and the starter works by feeding 12volts to the solenoid must be something with the switch or the main feed to that switch, or that wire that is feeding the solenoid from the switch. I don't know where that switch is getting its power but that is where I would be looking any bad connection could be causing a voltage drop. Could also be something in the 12 volt feed wire to the solenoid if it goes thru any other switches etc. What you really need is a wiring diagram.
You bridge pin 30 & 87 or 30 & 87a depending if it is a normally open or normally closed relay to bypas the relay
Test the relay by energising the trigger terminals
Most are not polarity sensative but again most relays have their circuit printed on the top of the cover
