You ran into a problem getting a riding mower or zero-turn to start. You can’t even get the engine to turn over. This is most likely because the starter motor isn’t getting the power to spin the engine.
A Simplicity lawn mower won’t turn over or crank when the battery is weak, the wiring and components are loose or corroded, the fuse is blown, the ignition switch is bad, the safety switch is faulty, the starter solenoid is bad, or the starter motor is bad.
Follow the safety precautions found in your operator’s manual. Always disconnect the negative black cable from the battery prior to performing repairs to the electrical system.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
Why Your Simplicity Mower Won’t Turn Over
Dead or Bad Battery
When your battery is weak, it won’t provide the power needed to turn over the engine.
To extend the life of a battery, you should keep it fully charged. This is very important when storing the lawn mower and battery. A battery that is not fully charged and stored in cold weather can freeze damaging the battery.
Test your battery using the steps in the article “5 Things That Are Draining the Life of Your Lawn Mower Battery”.
Charging a Battery: Use a battery charger to charge your 12-volt battery. Before you continue, wear protective gear to protect your eyes and skin from electrical shock. Follow these steps to charge your lawn mower battery with a charger:
- Access the battery and terminals. You may need to use a screwdriver to uncover the battery. Do not remove the battery from the casing.
- Connect the charging cables beginning with the positive cable first. This is the red cable or the one with the plus sign. Place the cable on the positive battery terminal.
- Attach the negative cable to the negative battery terminal. This is the black cable or the one with the negative sign.
- Do not touch anything that doesn’t have a rubber coating to prevent electrocution.
- Set the charger’s voltage and amperage level to the desired level. The average volt level for lawn mower batteries is usually 12 volts. More amperage charges the battery faster. Start with two amps and work up to no more than 10 amps. A slow charge is best.
If the battery fails to hold a charge it must be replaced with a new battery. You can purchase a new battery at your location lawn mower dealership, hardware store, or automotive store.
Bring your old battery with you. Most places will charge you a core fee unless you provide them with your old battery.
Loose Cables, Wires, and Connections
With the constant vibration of the mower, the wires and components can vibrate loose and no longer make a good connection.
Check the wiring and components on your Simplicity mower to make sure they are securely attached so there isn’t a break in continuity. Check over the electrical items for corrosion that can also affect continuity.
If you find corrosion on wiring, components, or terminals, first remove the battery cables and then the corroded components.
Try to remove this corrosion using a wire brush and a baking sold solution (2 cups water to 3 heaping tablespoons of baking soda). Replace the terminals if the corrosion is too severe to clean sufficiently.
A fuse is installed to protect your electrical system. Check your mower to make sure you don’t have a blown fuse.
If you’re unsure if the fuse is blown, you can check it by placing a multimeter probe on each prong of the fuse to measure resistance.
A resistance reading near 0 means your fuse is good. An infinity resistance reading indicates a bad fuse.
Replace a blown fuse with the same amperage as the fuse you are replacing. If you continue to blow fuses, you should bring your Simplicity to your lawn mower dealership or lawn mower repair shop to troubleshoot the root cause.
Bad Ignition Switch
When the ignition key switch is bad, nothing happens when you insert the key and turn it. Your mower will fail to turn over and start.
Check the switch using a multimeter to check continuity to determine if the ignition switch is the problem. To do this, look for the prongs mark B for Battery and S for Starter Solenoid.
Insert the key and turn it to the start position. With the multimeter set to measure resistance, touch one probe to the B prong and the other probe to the S prong.
A good ignition key switch will measure resistance near 0 ohms. A bad ignition key switch will measure infinite resistance and will need to be replaced.
Bad Safety Switch
Your Simplicity has an operator presence control system installed to keep you safe. A safety switch can be defective and cause your mower to fail to turn over.
Test your switch using a multimeter. You can also temporarily bypass the safety switch to identify a bad switch, but only do this for troubleshooting purposes.
Never operate a mower without the safety switch. Never run a mower when a safety switch is bypassed. A safety switch can save you from serious injury and you never know when you’re going to need it.
Bad Starter Solenoid
A starter solenoid is an electromagnetic switch that, when engaged, initiates the starter motor to turn over your engine.
The starter solenoid can go bad when the spring becomes weak or the copper plate begins to corrode. A weak starter, bad battery, or bad ground can also cause the solenoid to fail.
Before you test your starter solenoid, you must have a fully charged battery. Continue testing the solenoid by using the steps to diagnose a bad starter solenoid in “How to Tell Your Lawn Mower Solenoid is Bad”.
Bad Starter Motor
Once you have ruled out the battery, cables, wiring, ground, and starter solenoid as being the reason your Simplicity won’t turn over, it’s time to look at the starter. The starter can be removed and tested.
I recommend having your local repair shop that specializes in starter and alternator repairs test your starter and rebuild it if possible before just throwing a pricey new starter at your mower.