Parasitic drain, an automotive short circuit that may cause a recurring dead battery
I describe a practical algorithm for diagnosis and investigation of parasitic drain in an automotive electrical system. This problem typically presents with the recurring problem of a dead battery when the car is parked and not used for hours to days. Parasitic draw is a low amperage, high resistance short circuit that persists even when the ignition key is turned off. This video is published for entertainment purposes only, and it is not to be construed as an instruction guide. If you need help with an automotive problem you should carefully assess your limitations, and consider consulting a professional before getting in over your head. Be careful to protect yourself and to protect your property by not doing something you are unqualified to do....
November 30th, 2011 - 03:13
@spelunkerd You need a special low current clamp for anything in the mA range. Fluke makes a few.
November 30th, 2011 - 03:22
@eurokid83 it’s the (now discontinued) 1010i. I had to fix the switch once, when it failed to shut off. I believe it’s 1000A, 600V, Cat III.
Fluke have some new, stand alone clamp meters that seem better, though some of that may be advertising. I don’t find it great for the low amperage use in most automotive applications, though maybe it will be of more value with electric vehicles.
November 30th, 2011 - 03:44
Is that the 400 amp or 1000 amp current clamp your using in the beginning?
November 30th, 2011 - 04:42
Well done! All the way around! Great instruction, methods, and video technique!
November 30th, 2011 - 05:22
seen you around the etcg forums. great videos, subbed
November 30th, 2011 - 05:45
@eeiko321 Thanks.
November 30th, 2011 - 06:26
Very good video. 10/10
November 30th, 2011 - 06:34
So Document, Devide, and Conquer..Hmmm, kinda like the u.s wars in Afghanistan and Iraq..
November 30th, 2011 - 07:17
@batterybank I think that will work fine. Since parasitic drain is by definition a drain that is low amperage, it usually isn’t making a lot of juice because of circuit resistance. If circuit resistance is too high then a short detector may not have enough voltage drop to drive a buzzer. Higher amperage would probably blow the fuse in the fuse box, and so the problem would present as a recurring blown fuse.
November 30th, 2011 - 08:02
@spelunkerd I went aheadand installed he 4 amp fuse, I know AdrenalineJunky96 burned both his up. I just need to make up the connecters for the detecter. I wish the buzzer was abit louder.
November 30th, 2011 - 08:11
@batterybank That’s a good thought. I guess it would be one more ‘moving part’ that could fail and confuse the user if it suddenly blew. A reversible circuit breaker would work best, but I haven’t found one with such low amperage rating at my local hardware store. What I’ve built here seems to work pretty well. To me, the big weakness is a lack of ability to transmit a findable signal down a wire, a pulse wave modulator. But that adds expense and effort.
November 30th, 2011 - 09:00
Reguarding the amp draw using the 1 Ohm 10 watt resister, couldent a 4 amp fuse be added to protect the resister sence its only capable of 3.1 amps?
November 30th, 2011 - 09:06
@AdrenalineJunky96 Well I just went out and plugged the short circuit tester into the fuse panel under the passenger dash and replugged the connectors and expected the buzzer but I am getting nothing. I inserted fuse and retested under the hood and buzzer goes off. Stumped as to why the buzzer isn’t going off when inserted under dash?
November 30th, 2011 - 09:10
@AdrenalineJunky96 O.K. had someone tell me that the short would be under the dash before the fuse! So can I plug the tester into this fuse panel and plug/unplug and shake wires to narrow it down further? I have a strong feeling that it has something to do with the power door locks just because I have been in there. Am I correct in using the tester further with the connections before the fuse?
November 30th, 2011 - 09:18
@AdrenalineJunky96 So you are saying that the problem could be in the wiring even where I had disconnected the plugs/connectors? I thought by unplugging them and the buzzer continuing that it ruled out that area? So do I need to plug the detector device into the #2 fuse and start testing the connections again? Getting a little bit lost. Thx. Mike.
November 30th, 2011 - 09:33
Yah I had tried googling but nothing yet for the schematics. I thought by disconnecting the plug connectors that ruled out that area as the buzzing didn’t stop. So when I got to the fuse and it quit, I assumed it was between here and the wires running to the main fuse panel under the hood. Confused how 1 fuse in door locks and another is Lock Switch?
November 30th, 2011 - 10:15
@AdrenalineJunky96 Regarding where the fault is, it could be anywhere in the circuit covered by the #2 fuse, probably distal to the #2 fuse. Once you isolate the area involved, plug the other devices back in to get back to normal elsewhere. Try to find a schematic of the circuit involved — a google search might help. .
November 30th, 2011 - 10:16
So……. does this mean the problem is in a wire between this fuse and the larger 60 amp fuse in the engine bay? Is the “lock switch” between here somewhere? I appreciate your help as I know if I took to a mechanic i’d done spent a couple hundred bucks. I like doing things myself and though annoying it is good to see i’m on the right track….. MUCH THANKS! Look forward to more of your input!!!
November 30th, 2011 - 11:04
O.K. more progress but yet still so far away. I have a 94 Oldsmobile 88 Royale. I have unplugged everything I can find relating to trunk release, power door locks and horn as far as connectors go and shaken everything around them. I just found there is another smaller fuse box under the passenger side dash. There is smaller fuses for 1. Door Locks, 2. Power Antenna, Lock Switch, Trunk Release, and 3. Horns. I got to #2 fuse and WALAAAAAAAAAAAH, the buzzer quit!!!
November 30th, 2011 - 11:27
@AdrenalineJunky96 Oops, I replied to your first message before I read this one. If you pull the fuse on that 60A circuit for a few days, does the problem go away? The circuit of that home made tester is wired exactly per the schematic on my video. Maybe the resistance of your short is too high to give enough drop voltage across the tester to light up. Does it work if you wire the tester straight across the battery? You could use a simple test light. Strange problems are often due to bad ground.
November 30th, 2011 - 12:02
@AdrenalineJunky96 Two ways to approach this kind of problem. Most of us quickly go to what instinct tells us the problem is, like you did above. That approach is faster and often you get lucky. When that doesn’t work, I find the second approach is better. Go right back to basics and start from scratch, by first investigating, slowly and methodically. The car will tell you what is wrong if you hone your listening skills. I could be more specific, if you can accurately describe what you have….
November 30th, 2011 - 12:59
I just then went off the buzzer. I had recently replaced power window motor so thought it was probably the power door lock wires. I have disconnected the power door lock on the driver side door where I had worked. I unplugged the trunk release button and removed the plug in from the horn. I have wiggled the wires in these areas but nothing happens. Am I missing something? I greatly appreciate a reply.
November 30th, 2011 - 13:44
O.K. I have used the resistor and found that a 60 amp circuit which includes power door locks, horn, and trunk release is pulling a little over 3 amps and every couple days the battery is dead. I made a short circuit tester but my buzzer only works and it only works 1 way. The spade terminals have to be plugged into a certain side or it doesn’t buzz. The light doesn’t come on though and only has a hot wire. I was looking at the diagram. Do you not have the negatives wired to the switch?
November 30th, 2011 - 14:37
@captainbluejay Yes, if your resistor is 1 ohm, the amperage = voltage drop across that 1 ohm resistor. So, if you have it hooked up correctly then you are at just over 2 amps. Remember the hood light and the computer, and anything else you might have left on. If both of those are off (for long enough for the computer to go into sleep mode) you are way too high — should be in the range of 0.045 amps. My meter uses automatic range-finding.
November 30th, 2011 - 15:22
@spelunkerd I could not see your multimeter very well to see the setting selection.Should my cheap multimeter be set at 20 on the DCV selection? The reading will be in volts, which is equal to amps beacuse of the resistor.Is that correct? When I test at that setting I get a reading of – 2.13 with all lights off and the computer at rest. Does this mean my drain is just over 2 amps?