To check for ripple voltage from the alternator, the digital multimeter (DMM) should be set to measure what type of voltage?

To check for ripple voltage from the alternator, the digital multimeter (DMM) should be set to measure AC volts. Ripple voltage refers to the AC component that can be superimposed on the DC output of the alternator. When the alternator generates electricity, it converts mechanical energy into electrical energy, which produces a combination of both AC and DC voltage.

In a well-functioning alternator, the primary output is DC voltage, but there may be some AC voltage present due to the inherent characteristics of the alternator's operation. This AC component is referred to as ripple voltage and can indicate underlying issues in the alternator's rectification process if it exceeds acceptable levels.

Measuring AC volts allows the technician to assess the amount of ripple voltage present. If the reading shows excessive ripple voltage, it could suggest problems such as failing diodes or other components in the alternator that might compromise its efficiency. Therefore, setting the DMM to measure AC volts is essential for accurately diagnosing the condition of the alternator in this context.