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International Automotive Technicians Network
Re: Parasitic draw testing
Posted to Technical Discussion Forum on 6/5/2013 17 Replies

After doing parasitic draw problems for many years, I have come to the conclusion there is on one perfect way to do the job. Using the volt drop test across a fuse is a great way to get a direction, but it will not tell you the needed down and dirty actual current draw on the circuit. An inductive clamp will not tell you the actual drain from the battery either since they all will drift a little over a long period of time.

The only accurate way to test the current flow from the battery is to run that current through an amp meter, preferably a graphing meter. You also need a high current switch installed in a battery cable so you can drive the vehicle then switch the current flow through your tester and watch modules time out.

Another much needed tool is a scan tool that will access all of the modules on a vehicle. It is nice to know what modules are talking or not talking to each other, and pulling fuses is not a great way to find this out. You need a scan tool to do that testing with.

The last thing you need is patience and lots of it. Some times these kind of jobs can get on your nerves.

Albin Moore
Big Wrench Repair
Dryden, Washington, USA

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