My Riding Lawnmower Battery Is Good, But Will Not Start
Modern conveniences can ease the completion of simple tasks or frustrate the effort by requiring repair before use. While powered mowers reduce exertion and time spent cutting grass, they also use an electric starter to crank the engine and offer no alternative. Improper diagnosis may lead to installing incorrect parts. Parts for mower starter circuits can be expensive and are often not returnable. The starter circuit in a mower is straightforward and easily repaired.
A 12-volt battery can show proper voltage when tested in a static state, but fail under a load. Test the battery with a load applied to the system. Turn on the headlights and test the voltage at the battery or attempt to crank the engine while monitoring battery voltage. Good batteries will remain above 9.6 volts under load at temperatures above 70 degrees Fahrenheit. Any lower voltage displayed may indicate the need to charge or replace the battery. Any arcing or smoking at the cable to battery connections shows incomplete or corroded attachments.
Cables Wires and Switches
Check voltage at the starter motor connection with the ignition in the start position. Low voltage found here may signify circuit problems. Trace the starter motor wire back to any solenoids or relays and check voltage there. Good voltage going into a device, but little or no voltage coming out may pinpoint the defect. Assure good connections and voltage levels at the ignition switch before condemning a solenoid or relay.
The presence of battery voltage at the starter motor connection with no starter action taking place may indicate a defect in the starter motor. Tap lightly on the starter motor housing with the wood handle of a small hammer or similar object. This action may dislodge debris or restore a connection, temporarily returning normal function. Assure clean mounting surfaces for the starter motor housing to engine attachment. A loose or dirty attachment will interrupt the ground circuit for the motor.
A starter that engages the flywheel but refuses to turn the engine over may be defective, but the engine should be tested before replacing the starter motor. Check the mower engine for binding or seizing. Turn the engine in normal direction of rotation by hand if possible. A mechanical engine failure or normal compression could cause heavy resistance. Remove the spark plug (or plugs) and attempt to turn the motor by hand without normal compression. If the mower engine turns easily by hand with the spark plug removed, the starter is defective.
- "Electric and Electronic Systems for Automobiles and Trucks"; Robert N. Brady;1983