Parasitic drains can be measured with ammeters with the battery cable. Now the problem with taking the battery cable off to install the ammeter is that, sometimes electronic modules are the source of the parasitic draw. In this video, instructor Dave Hobbs talks about some other tricks for diagnosing these problems. He talks about the class two message monitor– a feature available on the Tech Two and also the Master Tech– which tells which module’s active and which module is inactive. He also goes on to cover using a parasitic draw tool in order not to disrupt the circuit while using an ammeter. Watch and learn how to use the class two message monitor or a simple knife switch for some neat tricks in diagnosing some stubborn, hard to find, parasitic battery drains.

This clip is an excerpt from the 210 minute comprehensive “A6 Test Prep Program” with Dave Hobbs, available from Automotive Video.