The Power Probe DMM and Parasitic Draw Test (PART 2)

Posted by Power Probe TEK on July 7th, 2017
Categories : Blogs

So now that you have verified that the vehicle has a Parasitic Draw, now what? Verifying that you have a draw is one thing, finding the draw… Well, that’s the second part. In the past, the way that you would locate the circuit causing a Parasitic Drain was to have your Digital Multimeter still connected in series and remove a fuse one by one until the draw disappeared. With all the electronics and modules inside vehicles these days, computer modules can “wake up” after going to “sleep” simply by removing a fuse and re-inserting it. You need to keep that in mind otherwise you could misdiagnose the concern.

We have found a better way of locating the circuit causing the draw. Instead of removing fuses and watching the amperage drop to a normal level on the DMM, we can perform a voltage drop across each fuse and determine the milliamp draw in that circuit using our fuse charts that we’ve created.

To do this, reconnect the negative battery cable back to the post and gain access to the fuse panels. You may need to close door latches or door pin switches in order to keep any interior circuits from activating. Also, keep in mind that since you reconnected the negative battery cable to the battery post, you will need to let the vehicle sit for at least 30 minutes to allow the modules to go back to “sleep”. After the vehicle has sat and all the modules have gone to sleep, place your DMM in the DC voltage setting and place the two leads across a fuse and record the reading. Anything over 0 volts would be considered a draw.

We have charts designed for each fuse type. To use the fuse voltage drop chart, locate the measurement recorded from the DMM and cross reference the number to the fuse rating. That will let you know the milliamp draw on that circuit.

Click here to download charts


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