Voltage-drop testing can detect excessive resistance in the starting system. High resistance in the starter motor circuit (power side or ground side) will reduce current to the starting motor. This can cause slow cranking speed and hard starting. High resistance in the starter control circuit will reduce current to the magnetic switch. This can cause improper operation or no operation at all.
A Sun VAT-40 tester or separate voltmeter can be used. The following steps outline a typical procedure for performing voltage-drop tests on the starting system:
Was this article helpful?