How Your Lawn Tractor Safety Switches Work

All tractors have them. And all tractor owners hate them. Yep. I'm talking about safety switches.

If you've ever turned the key to start your tractor and absolutely nothing happened...or if your tractor has shut down on you for no apparent reason, the problem may be related to safety switches. Today I want to take the mystery out of lawn tractor safety switches by helping you understand how they work, so that you can get back to mowing and enjoying your tractor.

One word of disclaimer: Though safety switches can be a nuisance, I urge you not to disable or uninstall them. They are there for a good reason. Your safety is important. Understanding how safety switches work will help you overcome the frustration they can cause.

The Craftsman R1000 Lawn Tractor
features 5 typical Safety Switches

I have put the following material into video form, and I will link to that video at the end of this post.

We'll use a typical lawn tractor as an example for our discussion: The Craftsman R1000. It incorporates 5 of the most common safety switches.

Safety switches perform two functions:

First, they shut down a running engine when safe conditions are not met. They do this by connecting battery negative (ground) to your engine's magneto (ignition coil), thereby shutting it down. And example of this would be getting out of the driver's seat while the cutting blades are engaged. That is an unsafe condition, so battery negative is connected to the ignition coil and the engine stops.

The second function of a safety switch is to disable the starting system, preventing the engine from starting. It does this by interrupting the flow of battery positive (12 volts) to the starter solenoid. This is that dreaded scenario when you turn the key and nothing happens. For example, if you turn the key but have not depressed the brake pedal, voltage to the starter solenoid is interrupted and the engine will not start.

Let's look at the wiring diagram (schematic) for the Craftsman R1000 to see how its 5 safety switches perform these two functions, starting with those safety switches that shut down a running engine.

The Driver's Seat Switch works in collaboration with the Brake Pedal Switch and the PTO Switch. Battery negative (ground) is connected at all times to the Driver's Seat Switch. So what happens when you get off the seat? Two things. First, battery negative is connected to one side of the Brake Pedal Switch. If the brake pedal is not depressed, then battery negative is connected to the ignition coil and the engine shuts down. On this tractor, then, if the engine is running, you cannot get out of the driver's seat unless you depress the brake pedal and lock it into position.

This diagram shows how the Driver's Seat Switch and the Brake Pedal Switch
work together to shut down a running engine by connecting Ground to the Magneto.

The second thing that happens when you get out of the driver's seat is that battery negative is also connected to the PTO (Power Take Off) Switch (the switch that turns on the cutting blades). If the switch is in the "on" positon (blades spinning), battery negative is then connected to the ignition coil and shuts down the engine. This tractor, then, does not allow you to get out of the driver's seat if the blades are engaged.

This diagram shows how the Driver's Seat Switch and the PTO Switch
work together to shut down a running engine by connecting Ground to the Magneto.

Another safety feature on the Craftsman R1000 is the Deck Attachment Switch. That is, the grass deflector chute must be in place. Otherwise, if the deflector chute is not in place, battery negative (ground) is connected to the ignition coil and the engine shuts down. On this tractor, then, if the deflector chute gets knocked off for any reason, the engine will shut down. Not all tractors have this particular safety feature.

This diagram shows how the Deck Attachment Switch connects Ground
to the Magneto if the grass deflector chute is not properly in place.

The final safety feature that can shut down a running engine is the Reverse Switch. When you shift the transmission into reverse, battery negative is connected to the PTO Switch. If the switch is "on" (cutting blades are engaged), battery negative will be connected to the ignition module and the engine will shut down. This tractor, then, does not allow you to mow grass while driving in reverse.

This diagram shows how the Reverse Switch works with the PTO Switch to
connect Ground to the Magneto and shut down the engine.

Now let's look at those safety switches that prevent your tractor from starting if certain safety conditions are not met.

Here's what's supposed to happen: When you turn the key to the "start" position, battery positive (12 volts) should flow to the starter solenoid which then engerizes the starter motor and gets the engine running. But that 12-volt current must first flow through three safety switches before reaching the starter solenoid.

First, the 12 volts of battery positive flows to the Brake Pedal Switch. If the pedal has been depressed, the voltage then flows to the PTO Switch. If the switch is in the "off" position, voltage can then flow to the Deck Attachment Switch, which, if the deflector chute is properly attached, will then flow to the starter solenoid, the starter motor will engage, and the engine will start. In other words, on this tractor, three conditions must be met in order to start the engine: brake pedal depressed, PTO switch "off," and deck deflector properly in place.

This diagram shows how 12-volt battery positive flows from the key switch through
3 safety switches before reaching the starter solenoid.

Summary:
Now that we've seen how safety switches function, either shutting down your engine or preventing it from starting, troubleshooting an issue with the safety switches on your particular tractor will be much simpler, and hopefully a lot less frustrating. Good luck.

Here's the video: