[SOLVED] 130mA Parasitic drain related to ROOM and BTN fuses

Discussion in 'Mazdaspeed 3 Troubleshooting' started by originalmarshmello, Nov 10, 2023.

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  1. originalmarshmello

    originalmarshmello Silver Member

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    Year/Make/Model: 2009 Mazdaspeed3
    Mileage: 166,450
    Location: Arroyo Grande, California
    Concern: battery started draining within a few days out of the blue
    DTC's: None
    Modifications: BNRS4, Autotech HPFP, HTP 3.5” intake, ETS TMIC, GFB t9002 hybrid BOV, turboxs DP + RP, Cobb CBE, Damond TMM + PMM, Cobb RMM
    Boss BE7ACP head unit, Kicker hideaway sub, kicker Amp, kicker speakers. (Redid the whole sound system - worked fine for thousands of miles, so I doubt it’s the culprit)
    ECU/Tuning Software: Accessport v3
    Tuner: Atenza Tuning
    Is the concern intermittent? No, seems to happen constantly.
    Can you duplicate the concern? Yes, let the car sit.
    Recent Repairs: new alternator along with “30-40k” miles JDM engine 17k miles ago


    Diagnostics: I have tested my battery (rated for 550CCA, showing about 500 CCA) and my alternator while it was installed, these both seem to be within spec. Alternator will keep the battery topped off to around 14.1v while driving.

    I then tested the fuses in the engine bay and determined that my current draw is going through the 15A ROOM fuse and the 40A BTN fuse. I did this by hooking a multimeter between the negative cable and negative terminal of the battery, closing the circuit for the hood latch switch, then pulling fuses.

    If I leave all fuses connected, the draw settles down to somewhere around 300mA, until after about a half hour it goes to 120mA. At this point, I pulled the room fuse. For a split second, current went to 30mA but immediately shot up to 200mA. I then pulled the BTN fuse and the current went down to 30mA, which is acceptable.

    All my interior lighting seems to be turning on and off when closing doors. The Trunk light, overheads, front roof lights, glove box light, and dash lights all seem to turn off after I close the doors.

    Possible Culprits: First, my 12v cigarette lighter port light is out. I immediately was excited because I thought I found something useful, but it turns out disconnecting it doesn’t change the voltage drain at all. Darn.

    Second, I saw on a Facebook group that one guy had a functioning alternator and battery, but when he let the car sit the alternator’s voltage regulator was bad and would drain the battery down.

    I then (with the battery disconnected) disconnected the B terminal cable off my alternator, made sure it was well insulated and not touching metal, and connected the battery with multimeter. After only a few minutes, the current had dropped down but I still saw the 120mA draw. I left it hooked up like that overnight, and in the morning still same reading. Logically, I then pulled the ROOM fuse which lead to current dropping to 30mA, this time with the BTN fuse still connected.

    At this point I am fairly stumped. I’m not sure if the alternator voltage regulator is bad but am confused as to why disconnecting it would change the current flowing through the BTN fuse… unless the BTN fuse had to do with the alternator circuit?

    What is the next step in diagnosing and searching for the drain? I appreciate your advice, time and input on this!
     
  2. originalmarshmello

    originalmarshmello Silver Member

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    Does anyone have or know where to find electrical diagrams showing what circuits run off the fuses? If I had one of those I could at least have some direction to test components to see where my electricity is going.
     
  3. Awafrican

    Awafrican Moderator Silver Member

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    All those diagrams and work shop manuals are hosted in the metal member section.

    I'm not a electrical guru by any means but I know my center console cigarette lighter power is always on and if I don't want my battery to die over a long period I have to unplug my phone charger even if it's not in use.
     
    Awafrican, via a mobile device, Nov 11, 2023
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  4. Cfoldone

    Cfoldone Gold Member

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    Passenger Junction Block is (at least my 07 & 08) behind and below the glove box. The fuses you are looking at feed the PJB.
    Metal Membership is a great investment for the manuals. The PJB might be your troubles, and good electrical diagrams are a must for your year model. I am not sure when the shift to next gen speed 3 was done, so get your specific model diagram to work with.
     
  5. originalmarshmello

    originalmarshmello Silver Member

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    I got the metal membership (I needed to renew it anyways so good timing) and looked into the PJB. On my 2009, when I unplug the PJB the draw goes to right around 30mA. I tried pulling all the fuses in it but none of them affect the drain as far as I can tell.

    I’m guessing at this point the PJB might be faulty and defective… Has anyone else had their PJB fail and cause a drain? All my electrical systems in my car do seem to work fine, so maybe something on the sleep side of the system is shorted and not working
     
  6. Cfoldone

    Cfoldone Gold Member

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    In my case. I had a sneak current draw too. My 07 speed 3 was a Bose system. I also did circuit by circuit check of PJB and it was interior common circuit. Which goes all over. Figured same results.. Replacement? Not cheap and junkyard would have to find exact build sheet options...just gave up and did low settings charger. Then I decided to remove audio system head unit. Found that the cd changer was the culprit. Removed it, problem went away. I know yours isn't same...just thinking out loud.
     
    Cfoldone, via a mobile device, Nov 28, 2023
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  7. originalmarshmello

    originalmarshmello Silver Member

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    I forgot to update y’all but I noticed some loose wiring when I reinstalled my PJB the other day.

    Previous owner seems to have failed basic wiring class and there was one black with orange wire completely disconnected, which may have just recently come loose causing some of this. Here’s a photo for reference. Definitely some suspicious aftermarket wiring.

    I soldered the wire back together properly and shrink wrapped it, but now I have a new rabbit trail to chase. Wish me luck!
     

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  8. Cfoldone

    Cfoldone Gold Member

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    A surprise I found was a very old likely installed just bought from Mazda.. wires were spliced into loom harness left side under dash. Followed back and found this. Very first style of alarm with cellular radio access. Was interconnected to key switch... it didn't actually cause a fault. Was tracing out ALL unknown suspects in wiring. Speed 6 had a remote fob control box connected all over. Especially be suspicious of any inline "compression+flag terminal add a tap. They can slice though the wire causing less current or flaky electrical connection. IMG_20200516_152017.jpg
     
    Cfoldone, via a mobile device, Nov 30, 2023
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  9. originalmarshmello

    originalmarshmello Silver Member

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    IMG_0770.jpeg So I went through and tried disconnecting all the fuses from the PJB, no luck. I then traced out this aftermarket remote start system which I didn’t realize was there, and I was sure that had to be it… still nothing.

    Now, I’ve narrowed it down to this connector on the PJB. If I unplug it, the drain goes away down to 30mA. Normally, one would then backprobe the wires to find the culprit, but in this case the harness clip literally covers half the wires from being accessed. :/
    Does anyone have any ideas of how to find this drain? I 50% think my PJB failed somewhere and 50% think it could be some wire grounding out in one of those systems attached to the harness. image.jpg
     
  10. Cfoldone

    Cfoldone Gold Member

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  11. originalmarshmello

    originalmarshmello Silver Member

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  12. originalmarshmello

    originalmarshmello Silver Member

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    Long story short I accidentally discovered that it was related to the passenger door sensor. It worked enough to turn the light on the dash off, but not enough to tell the computer to go to sleep.

    I tried cleaning out the contacts with maf cleaner and it worked for the night, but kept going back once I would drive it. Had to replace it. It also just so happens that by that point my battery was shot, so I had to replace that also.

    happy that I finally fixed it!
     
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  13. Easter Bunny

    Easter Bunny Professional Engineer Motorhead Platinum Member

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    I had that one go bad on my car as well thankfully I was able to notice because the light would stay on once in a while
     
    Easter Bunny, via a mobile device, May 13, 2024
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