What is meant by a parasitic draw in an automotive context?

A parasitic draw refers to a small current draw on the battery while the vehicle is turned off. In automotive electrical systems, this phenomenon is a concern because it can lead to battery drain when the vehicle is not in use. Various electrical components in the vehicle, such as lights, radios, security systems, and computers, may continue to consume power even when the ignition is off, which is why identifying and measuring parasitic draws is crucial for ensuring the battery retains sufficient charge.

When diagnosing electrical issues, particularly battery draining problems, understanding parasitic draws helps technicians pinpoint what component might be causing the excessive current draw. Generally, a parasitic draw that exceeds a certain threshold can indicate that there is something in the vehicle that should be off but is still drawing power, highlighting the need for further investigation to rectify the issue.