The seat switch along with the two control lever switches, and the parking brake switch all work together and have a dual purpose that is coordinated by the ECM, electronic control module.
Initially, cranking of the engine will not happen unless all switches are in the correct position and the seat switch has been actuated by the operator being on the seat. Conversely, a running engine will stop when the operator leaves the seat unless the control levers have been positioned outward fully and the parking brake has been engaged.
The vertical position of the seat switch puts it in a spot where it gets dust down into it. When the dust accumulation is too much, then cranking becomes intermittent as the dust affects the electrical contacts in the switch. Many other makes also have this same problem.
I have added ground bonding cables to my Tiger Cub from the negative battery terminal to a frame grounding point and from a vacant bolt hole on the engine to another frame ground. If you add bonding cable to your engine make sure that the bolt is not too long to where it will brake a hole into the crankcase when tightened. There are usually several unused bolt holes on an engine but check to see if the threads are metric or SAE, usually metric but not always.
I keep a spare seat switch in my parts stash, but I also have installed a switch in parallel to the seat switch that when needed I must get off the machine, raise the seat, and actuate the switch manually to get the engine to crank for starting.
I have also cleaned every electrical connection on the machine as they are subject to corrosion and dirt. Disconnect the battery first if you decide to clean the connectors.
The wiring diagram for my Tiger Cub model is incomplete as it doesn't show where the battery power is connected into the system and doesn't show where the charging system is connected. I have written to Scag about this but have not as yet heard back from them. There is no diagram for the ECM but this is normal as it probably is a proprietary item, but the ECM manages all the low current electrical system by reducing the number of switches needed in the system and without it nothing electrically happens.
Batteries on these machines are also subjected to lots of vibration and sometimes internally can break down. I periodically put a 2 amp charger on all my batterys and this helps them live longer, but usually don't get more than 4 years out of them. The electric clutches on these machines draw 4-5 AMPS when engaged so having a battery and charging system fully functioning is a good thing!!
Mad Mackie in CT:biggrin::laughing: