The BEST Way TO Perform a Parasitic Draw Test

Parasite current draw tests can be a nightmare. When a car has battery drain proper testing is vital to finding the problem. This is the best way I have found to perform a Current Draw Test!

Join me as we discuss:
~ Equipment needed for test
~ Proper Battery voltage
~ Testing DVOM leads
~ Prepping the car for PID test
~ Measuring fuses
~ Using the current draw chart
~ Isolating the circuit
~ STOP PULLING FUSES!

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disclaimer:
The content of this video is available for informational and educational purposes only. It is not intended to be a substitute for the professional advice of a mechanic who has personally inspected your vehicle, nor does it create a relationship of any kind between the Humble Mechanic and you. Every situation may be different, and the Humble Mechanic does not make any warranties, whether express or implied, as to the accuracy, fitness, or applicability of the information or automotive parts portrayed in this video to any project and makes no guarantee of results. The Humble Mechanic and any sponsors of this video will not be liable for any damages related to personal injury, property damage or loss of any kind that may result from the use or reliance on this video and/or any automotive parts represented in this video. You are using the information and automotive parts portrayed in this video solely at your own risk.

[steveacker]

I chased a parasitic draw on my 2010 Ram for months. I even took it to a dealer and a local shop after I failed to find the culprit. They couldn't pinpoint it either. I checked everything...or so I thought. Just by dumb luck, I dropped something in the driveway at night and it rolled under my truck. I glanced up and saw a faint light in the engine bay.
Turns out that the hood latch (and the hood light actuator/switch) was slightly askew. The hood would latch, but since the latch was out of position, the light switch never disengaged. Makes sense that this light would never show a draw as I would disconnect the hood light at the bulb connector since I had the hood open testing for current draw. Crazy stuff, but I learned a lot from videos like this one. Hopefully, my story helps someone out. Thanks!

[jc]

This guy was clean shaven when he started looking for the draw.

[bikerdave]

I've been a master tech for 25 years and never once did I think about physically latching the doors etc. And this is a great method for finding gremlins. I'm glad I found this channel, as unusual even as good as I am in still learning! Awesome video

[clintlambert]

I’ve used this method with success several times. I’ve recently learned an extra hint to go along with this test. Prior to testing each fuse(especially with vehicles with a large amount of fuses), use a thermal image camera to look at the fuses. The one with the draw will show up warmer than the rest. Helps pinpoint the circuit quickly.

[jeffclark]

Some of the new fuses now don’t have the test spots on the back because engineers decided that was too handy and they pride themselves in making things more difficult for us mechanics. Great video man

[freddydee]

I've been a tech for over 25 years.
I thought I was pretty good at electrical diagnostics.
This video set me straight.
What a great technique.
Thanks for these videos.
I wish these were around in the 90's.

[dannydee]

I've been a master tech DIYer, weekend warrior, shade tree mechanic, jack of all trades master of none, under sensai mr Miyagi, for the past 30 years never ever seen such a great great video'. Thanks!

[ronanrogers]

For new viewers, just an observation that 1006 milliamps is just over 1 amp, not 0.1 amp as was said at 7:06. Humble Mechanic has acknowledged that he mis spoke in old comments below.

[mikewest]

When I worked as a diesel mechanic it was always aftermarket shit. Even high end GPS trackers that were tamperproof. Always start with aftermarket add ons.

[Viper]

I feel we are blessed to have you and several others on YouTube sharing your knowledge with us . Those who do not wish to learn and those jealous of your knowledge and capabilities will always try to discourage others . I am 51 and wish training videos like yours were available when I was in my teens . Truly truly helpful . Thanks for all your work .

[scottellis]

Best parasitic draw video out there. One note: good test leads are not cheap. If your multimeter does not read zero ohms, Fluke says that is just increasing resistance as the meter electrical contacts, and the lead connections get dirty or corroded over time. If cleaning with contact cleaner, or isopropyl alcohol doesn't work, you can use the "relative" button on the meter to adjust for the increasing resistance. Set to ohms, touch the leads together, push the "relative/rel" button, and the display will read zero. Fluke says you only need to throw the leads away when the wires become exposed, or broken.

[andrewhaney]

One small correction to note. 1006 in speaking of amps is 1.006A not .1A, simple mistake but for students it could be detrimental when they are struggling to understand 1000mV is 1V ect. Good video, glad to see other putting things out like this to help promote the industry.

[ihna]

Had a draw on a skid steer. Not as much out there for help with equipment as there is for automotive. A fuse panel is a fuse panel so I administered your test and used in line amp draw method. Ended up being a bad starter. Thank you for taking the time to share the knowledge

[mcdemos]

This guy is easy to watch and always adds little touches of experience that simply following an instruction manual doesn't give you. Always good to see a Humble Mechanic video appear in my Google search results...

[klyddmeisters]

Its very important to check fuses before start metering. If a fuse is blown you might have 12v on one side and ground on the other (through a windshieldmotor or windowheater etc) and your multimeter might get damaged when measuring up to 300mV. Set meter to 20v dc atleast and do this test before switching over to 300mV.

[dneedham]

Thank you so much for this video. My daughter's '06 Beetle convertible developed a parasitic power drain over the past month or so. Following your procedure I narrowed the power draw down to fuse 38. Driver and/or Passenger Door Control Unit. After sitting for 2 hours, fuse 38 was pulling about .8 amps. We had an issue with the driver side door about two months ago where the window wouldn't drop sometimes when opening, and then it wouldn't go back up. Dealership diagnosed it has being out of adjustment. It has been performing normally since then. Before locking the door mechanisms for the diagnostic procedure, I decided to remove the driver side door panel so I could have access to the window motor connector. After two hours of waiting, I verified there was still an approximate .8 amp draw from fuse 38. I unplugged the window motor and the draw went to 0. I plugged it back in and it went back to .8 amps. I may be mistaken, but I think I smelled a slight burnt smell from the window motor control unit when I unplugged it. I think this is the culprit. I am going to order a new motor tomorrow morning and see if this sorts it out. Thanks again!

[andik]

Great video and information. I personally disconnected the battery + and put my amp meter between the plus and the plus cable (10 A setting). I looked the doors and after the car went to sleep I saw a parasite draw of 250 mA. I reconnected the battery locked the doors and checked every single fuse like you did in the video. No draw found. I disconnected the battery again and hooked everything up like before. Then I disconnected the alternator lead from the alternator and the draw was 25mA. So my parasite draw was from the alternator. Since the alternator in my car is not fused I wouldn't be able to find the fault with your method alone

[b_gumm]

Electrical Engineer here; didnt realize that fuses has a large enough resistance to them to detect a significant enough voltage drop to calc amperage off of. Interesting technique. Thanks.

[wouterkellerman]

42 years as a mech and never knew this. Thank you!

[socram]

For older cars, you may have to tape the door ajar button on the door frame instead of flipping the latch.