Ask the Expert: There is an excessive current draw when I did a parasitic draw test. Now what?

Feb. 27, 2016
If a vehicle has an excessive amount of current draw, you will need to locate the circuit that is causing it.

Q: There is an excessive current draw when I did a parasitic draw test. Now what?

A: If a vehicle has an excessive amount of current draw, you will need to locate the circuit that is causing it. The old way to locate a circuit with an excessive draw was to leave your digital multimeter hooked up (set to amperage) in series and pull fuses until the reading falls to an acceptable level. Due to the amount of electronics in today’s vehicles, pulling fuses could cause modules to wake up and give you false readings. A different method to locate a circuit with an excessive draw is to measure the voltage drop across the fuse. This will allow modules to still be asleep while testing the circuit. Before testing, always make sure that the battery is fully charged and that any accessories have been removed from all power outlets, all lights (vanity mirror, dome lamps) have been shut off, and all doors closed or latched. (If you need any doors open to gain access to interior fuse panels, set the door latch in the closed position or disable the door pin switch.)

First, set the digital multimeter to the millivolt range. Then probe both terminal of the fuse you want to test at the same time. If you have any readings above zero you should note down and determine how much current is going through that circuit by using our fuse charts available for download at http://info.powerprobe.com/fusecharts. Once you have found the circuit that has excessive current flowing in the circuit, you will need to trace and locate the component or accessory that is causing the draw. Also, don’t forget to check for technical service bulletins for any information. Technical service bulletins provide valuable information that could save you time and headaches.

Information provided by: Power Probe

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