Ride around lawnmowers are very useful when they are running properly. They can be very frustrating when they fail to start, do not run smoothly, or have some other problem. In this article we will look at how to diagnose and repair some of the common electrical starting problems that may occur in your ride around lawn mower.
In a typical ride around lawn mower the primary role of the electrical system is to provide energy to drive the starter motor and the high voltage to provide a spark in the the cylinder head. While there are a number of different designs most often the ride around lawn mower has a lead acid battery similar, but smaller, then a car battery. A +12 volt electric system is assumed for this discussion. Through the use of a starting solenoid the battery is directly connected to a starter motor which is used to rotate the engine during starting. The ride around mower starter motor can provide the torque necessary to spin the engine, which is typically engaged by means of a moveable gear. This gear is only engaged when the starter motor is being used.
The ride around lawn mower starter solenoid is basically a relay switch that closes some conducting contacts when voltage from the battery is applied. The voltage applied is low current since it is only engaging a small relay coil in the solenoid. In turn the magnetic field of that coil causes the heavy contacts to close. These contacts are designed to handle the heavy current used by the high torque starter motor. A heavy gauge wire from the positive pole of the battery is connected to the solenoid. Another heavy gauge wire goes from the solenoid directly to the starter motor. When the engine starts the starter motor is disengaged and the solenoid opens when the starter key is turned from the START to the RUN position.
One common electrical problem encountered in ride around lawn mowers is when the starter key is switched to START and the starter motor spins slowly or chatters. Quite often this can be interpreted as a problem with the starter motor or starter solenoid. While this can be the case it is likely that the lead acid battery is either partially discharged or one of the cells in the battery is dry or the battery damaged or beyond its useful life. The quickest way to check this is to use jumper cables to try another similar lead acid battery of equivalent voltage in parallel to the original battery. This can be a car battery if the voltage is the same. If using another battery causes the starter to spin rapidly and turn over the ride around mower engine you should then try recharging the ride around battery. If charging does not solve the problem then replacing the battery is called for.
On occasion the starter solenoid will develop a problem. When that happens turning the ride around mower key to the START position may produce a clicking noise or no noise at all. In either case the starter motor does not spin properly or at all. The starter solenoid will have heavy wires attached to it. These are wires from the battery that also go to the starter motor. A smaller gauge wire going to the starter solenoid delivers the battery voltage needed to engage the heavy starter solenoid relay contacts that apply the battery voltage to the starter motor. The small gauge wire should connect to the key module. Turn the key to START and using a volt-ohmmeter check to see if +12 volts is temporarily applied to the contact on the side of the starter solenoid where the small wire is attached. If +12 volts are measured when the switch is turned to START but the starter solenoid does not cause the starter motor to rotate you can investigate to determine if the ride around mower starter motor is functioning properly. You can check this by using jumper cables to an external battery to apply voltage directly to the starter motor. If it spins properly it should be OK.
The focus should then be on the ride around mower starter solenoid. Attach the volt-ohmmeter to the small wire terminal on the solenoid, disconnect the small gauge wire from the key switch and apply the voltage from the external battery directly to the starter solenoid thus bypassing the START switch. If the starter solenoid does not engage the starter motor then it is likely the starter solenoid is bad and needs to be replaced. If the external battery causes the solenoid to function and the starter motor to spin the following should be investigated.
If +12 volts are not found going into the ride around motor starter solenoid when the key is turned to START, place the probe of the voltmeter on the START contact of the key switch. This should have the same color smaller gauge wire as is found going into starter solenoid. When you turn the key to START if no voltage is found then it is likely either the switch is bad or the wire going into the switch that delivers the +12 volts is not connected to the battery. This can be traced using the volt-ohmmeter. If there is +12 volts going into the starter switch but +12 volts does not appear when the switch is in the START position then the switch may be faulty or the contacts corroded and not making good contact. Bypassing the switch with a jumper wire can test this. If the engine turns over then the switch is defective. If the engine still does not turn over it is likely there is a problem in the wiring between the switch and the starter solenoid.
To determine the source of the problem connect a wire directly from the starter switch to the small gauge wire terminal on the ride around mower starter solenoid. If turning the switch causes the motor to spin start tracing the path of the wire. You will likely find it runs from the starter key switch module to another switch that may be set up to only be closed when the mower blade is not engaged. Similarly there may be another safety switch that only closed when the transmission is in neutral. These safety switches can malfunction or their alignment can change with use. The contacts can also become corroded and no longer provide a reliable connection.
Now that you have the problem area narrowed to the wire between the starter switch and the starter solenoid it is a matter of testing these switches independently by using jumper wires, your volt-ohmmeter, and a little patience and ingenuity. While it may be tempting to bypass these safety switches with a wire or jumper this is not recommended since they provided a needed level of protection to the mower operator.
By following an organized approach to testing using a volt-ohmmeter certain electrical problems on ride around lawn mowers can be diagnosed and repaired.