The ability to detect, observe, and measure electricity is crucial when trying to understand how a tractor works and learning what you can do to fix it. The digital multi-meter is like a doctor’s stethoscope. It allows us to see the invisible force of electricity and measure how it interacts with the components in our engines and tractors. A digital multi-meter measures current (amps), voltage (volts), and resistance (ohms).
Most of the circuits in lawn and garden tractors use low amperage with the exception of the starting circuit. The wiring also only runs a short distance. I recommend using 6 AWG wire for the high amp starting circuit, and the negative side of the battery to common ground connection. All other wires can be 16 or 14 AWG. The easiest and most effective way to make all of the connections is by using nylon wire crimp connectors. Nylon wire crimp connectors are more durable than ones made from PVC. They are also easier to install than soldered connections. The most common crimp connectors you will use are spade and ring connectors.
Measuring resistance can indicate the health of a component. For example we can determine if an ignition coil is healthy or not by measuring the resistance of its windings. To measure resistance, set your meter to Ω ohms resistance. If you need to select a range, select the smallest range normally 200 ohms. Place the red probe onto one of the small terminals of the ignition coil, and the black one on the remaining small terminal. Your resistance will then display. A normal ignition coil should read about 3.5 to 4 ohms. If your meter reads a much higher resistance it means your ignition coil may have a short and is faulty.
To measure voltage on a battery for example you first turn your meter to DC Voltage. Place the red probe on the positive terminal of the battery and place the black probe on the negative side of the battery or on a common ground. Your voltage will display on the screen.