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*Updated: 02/06/2022 5:26PM PST

Need ideas and/or confirmation - electrical issue


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Hi everyone... I am presently troubleshooting a parasitic draw issue that manifested itself this morning because outside temp went to -21c... I am searching for 0.3A draw and I have found it coming from fuse 56. This is one of the 3 fuses responsible for the rear defogger....  The problem I have is with the logic of what I am finding while troubleshoothing this...


Here's what I am doing and what the results are.


1) Remove the fuse = the draw goes away

2) with the fuse back, if I remove the Rear window defogger relay #E117 = The draw is STILL there !


Is it safe to think that somehow between the battery and the fuse, this R/W wire is finding a ground ? 

Am i wrong to think this ?


How would you go about this ?


I'm looking for any advice from anyone who has troubleshoot an electrical issue.


Thanks again.



Edited by fleurys
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Simple. There is something else on the same circuit. If you dig through enough of your wiring diagrams, you will find that fuse is powering more than just the window defogger. 


Is the draw constant, or does it go away after 10 min or so. With modern autos, you need to wait a while after connecting the battery to do a parasitic draw test to let all the modules shut down. 

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Thanks for taking the time to help guys... really appreciated....


Before I continue, this is a 2003 LE with vdc and navi...


I have a couple of hours in on this and you can tell me if I'm doing it wrong...


Here's the summary of the power distribution diagram :



so it seems it is only doing 2 circuits... LOAD and DEF.


Here's the details of the power diag



so again, in details , it is EC-LOAD and EL-DEF circuits.


Here's EC-LOAD diagram...



This shows me, regarding fuse 56, that in conjunction with the EL-DEF diagram, the power is really not being consumed by any other device then the rear defogger circuitry..  


My theory about a mistery ground between the fuse and the relay (not the battery and the fuse like previously stated) is based on the fact that when disconnecting the D305 Ground (the ground for the defogger), nothing changes in the current draw.


So my nect step this morning is to trace the wire from the fuse box to the relay box.. I'm thinking it's picking up a ground along the way... I will also confirm that the pin 5 (wire B/Y) on the other side of the relay has no power when the relay is removed... This will confirm me that the issue is not within the relay box itself...




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One more thing...  There was an old and problematic remote starter installed before I bought the truck... It was always acting weird and last night I decided to remove and clean everything... I'm thinking that maybe the rear defogger circuit was piggy back on for the remote starter... Would it make sens ?  I never installed a remote starter, so I do not know, but it would seem logical for it to attach to it....


If you think my approach is wrong, don't hesitate to talk ! LOL..  


One last thing to note, is that when this fuse (56) is off, the current draw is 13ma...so I know once this is figured out, i'll be golden...

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OK... the truck is fixed... Here's my findings and reasoning if it can help others...


So having confirmed that the fuse 56 is only being used for rear window defogger, and that removing the Rear window defogger relay (The first point of connection in the circuit) did not stop the parasitic draw, I decided to isolate the R/W (red with white stripes).


I disconnected the battery then What I did is apply direct battery voltage to the fuse pin (under the fuse while it is removed), and measured the voltage at the relay box side on pin 5 (while the relay is removed). I measured 0.4 volts less than what the voltage that was put in... That confirmed me that I had also the right wire and that it was going directly from the fuse box to the relay box... 


One thing I tried is to measure ohm resistance on the wire but it showed 0 ohm resistance... I'm not sure what to think of that since my 12v was shorting to ground somewhere..maybe someone can explain this result...normal ??


So having the confirmation that the wire was picking up a ground along the way between the fuse box and relay box, I was not very interested of pulling the harness and opening it and doing tests along the way to try to find the break in the wire or whatever was the issue... If it is a rubbing issue and that the harness has been exposed to body ground, I know I will probably have to have a more thorough look in the future as I expect new parasitic draw to come my way, but I am taking a chance...


So basically, I dismantled the fuse and relay box, cut the R/W wire and spliced a new 14g wire going on the firewall side. The problem is now gone and the draw is now about 13ma...  Big change from .335ma at the beginning.


I learned quite a bit about electrical troubleshooting in this one...







Cheers .


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That is odd. I'd be surprised if a rubbed wire was giving you a high-resistance short rather than a dead one, unless maybe it was shorting through some other circuit (or like you said, somebody tapped the remote start into the first hot lead they found). I chased a mystery high-resistance "short" in the headlight circuitry on mine that turned out to be the high-beam indicator on the dashboard.

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