There are basically 2 safety circuits on this tractor. One affects the starting and the other deals with operator control.
The starting safety circuit ensures that the machine is immobile and that the blades are off to prevent injury. This circuit starts at the ignition switch on terminal "S". When you turn the key to the "start" position voltage is sent from the ignition switch to a switch on the clutch/brake. If that clutch/brake is pushed or locked down, voltage is allowed to pass through to the PTO switch where the same thing is determined. If the PTO lever is up, voltage stops there and the starter is never engaged. If the lever is down, voltage is allowed to pass on to the starter solenoid where the voltage will engage the solenoid and allow a contact to be made to engage the starter and spin the engine over.
The "operator presence" safety circuit works (more or less) between the PTO safety switch, a safety switch on the seat, and the clutch/brake switch. What it is looking for is the seat switch being triggered. If you are on the seat, you can start the blades. If you are not on the seat and you attempt to start the blades, the system is grounded out and the engine shuts down. The same actions take place for the clutch/brake. If you are not on the seat (switch not triggered) and the clutch brake pedal is lifted, the engine will shut down. All this works on the idea that a bad situation can get a whole lot worse if the machine does not stop doing what it's doing if something bad happens. If the tractor turns over, the engine is going to die. If you are not on the seat, it is assumed that you are no longer in control of the machine and it needs to shut down (quickly) to prevent further injury.
The safety circuit on this mower is quite simple and very effective at doing what it is designed to do. I know that every year people try (and some succeed) at bypassing the safety features. In way too many cases, the outcome of that is terrible. I cannot possibly stress enough how important it is to
tamper with the safety circuits. We get reports all year long of situations where people have been maimed or killed because the safety circuit was bypassed and the blades did not quit turning when they should have. It's very easy to assume that I know what I'm doing on a tractor and I don't make mistakes. That's human nature to make that assumption about something you do weekly. But accidents are called accidents because they are just that. If they were normal, they would not be called accidents.
A quick story of my own to demonstrate how easy it is to just not think when something very abnormal happens. My house back home as 10' glass doors all the way across the front of the house. I've mown that yard well over 100 times. I came across that stretch one afternoon and caught a rock from someone and sent it through that window. One of my nieces was sitting just on the other side of that window when it crashed in. I was moving and the tractor, saw the glass go everyone and immediately stood up to get off and go check on my niece. Had the safety circuit been bypassed (because I do know how to do it), I would have likely lost a foot when I stepped down because the 50" deck does not know my foot is there. The safety circuit caught the fact that I had left the seat and immediately stopped the engine. Everybody was ok and I just had to replace an $800 window.
I work on these machines a lot and I came right off the seat and never though another thing about it. It is human nature to make those sort of mistakes and the manufacturers to the best they can (within reason) to help us not hurt ourselves.
So, that's my safety circuit speech. If you are having problems with yours, please reply back to me here on this thread and I will help make sure yours is working as it should be.
Thank you for using Manage My Life!