Starter Voltage Drop Test
Voltage drops in the Starter circuit can be very difficult to find and cause you many hours of frustration. We hope that the following diagrams will help you troubleshoot the Starter system.
Some key points to remember are:
- Any added resistance to the starter circuit can result in decreased starter performance.
For example, with a system drawing 200 amps during cranking, when we add 0.01ohms resistance to the starter circuit, we will reduce the voltage in the system by 2 volts. This degrades the starter's performance and life span.
- When performing voltage drops always have your positive lead of the multimeter on the connection closest to the battery.
- When performing voltage drop tests current must be flowing in the circuit. This means the engine must be cranked.
Step 1. Starter Voltage Drop - Positive Circut
With positive lead of the multimeter touching the positive (+) battery post (not the cable end) crank engine while watching the voltmeter (wired as shown above). Reading on voltmeter should be less than .2 volts.
If reading is more than .2 volts go to step 2. In step 2 we will check the components of the positive (+) circuit.
Step 2. Starter Voltage Drop - Positive Circuit Components
Connect (+) test lead to battery post, and (-) test lead to battery cable clamp.Then check for voltage drop at this connection.
Check each component and link in the circuit while cranking the engine. Those components with a voltmeter reading of greater than .2 volts should be repaired or replaced. Check the component or link to verify that the voltage drop is now .2 volts or less. Check across every connection, cable and component.
Step 3. Starter Voltage Drop - Ground Circuit
With negative lead of the multimeter touching the negative (-) battery post (not the cable end) crank engine while watching the voltmeter (wired as shown above). Reading on voltmeter should be less than .2 volts.
If reading is more than .2 volts check components in the ground circuit. Check components just like we did in step 2 but place the negative lead from multimeter to the connection closest to the negative battery post.