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Thread: Parasitic draw on battery when parked.

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  1. #1
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    Default Parasitic draw on battery when parked.

    I have a 3 month old battery, and when I went to start my car yesterday, the battery was completely dead. It would barely flash the anti theft light. It was only a few nights ago, since I drove it. It ran fine, had bright lights, and the voltage gauge was reading normal.

    I charged the battery, and disconnected the ground. Then I put my multi meter between the ground cable and the negative post of the battery. With the key off its reading almost 12 volt. 11.49 ish. I pulled every fuse and relay one at a time and seen no difference in the reading. I even disconnected the relays to my electric water pump and the 40 amp back to my BAP and FPDM. I also disconnected the charge cable at the alternator

    I have no idea where the draw is coming from? Possibly the main power cable to the starter or an internal short? Kinda lost on what to test next?

    As always any ideas will be appreciated.
    2000 Mustang GT SOHC 4.6L : 665hp at the tirel
    11.00 @ 134 mph... A 17 year love affair...


    Wyotech Graduate 03/14 : High Performance 1 & 2...Engine Management Systems 1 & 2...Powertrain...
    Chassis/Suspension & Braking systems.. 3.7 GPA.

  2. #2
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    Default Re: Parasitic draw on battery when parked.

    Don't you need to hook up an amp meter instead of volt meter?
    JP
    Bigger, Stronger, Faster...

  3. #3
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    Default Re: Parasitic draw on battery when parked.

    Yes lol you do. I was retarding out.

    I think I must have an issue with my meter. If I check for volts between the ground cable it reads about 12, but if I put it to A-dc 20 Ma and try and get an amp reading, it reads zero. If it reads volts why wouldn't it show any amps?

    Another weird thing was when I first took it out for a tonight my mileage was not showing on the dash. After half a mile it just came on. It wasn't the dashes like some people get when they're having ECU issues it was just blank.
    2000 Mustang GT SOHC 4.6L : 665hp at the tirel
    11.00 @ 134 mph... A 17 year love affair...


    Wyotech Graduate 03/14 : High Performance 1 & 2...Engine Management Systems 1 & 2...Powertrain...
    Chassis/Suspension & Braking systems.. 3.7 GPA.

  4. #4
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    Default Re: Parasitic draw on battery when parked.

    I've always used a clamp-on type, so I'm not sure with your type of meter.

    I have no idea on the odometer issue.
    JP
    Bigger, Stronger, Faster...

  5. #5
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    Default Re: Parasitic draw on battery when parked.

    Well I went and tried to measure the amp draw and wasn't getting a reading. The multi meter has 2 fuses one is a 200 Ma/250 volt and the is 10A/250V. The 200 Ma is blown and I'm having trouble. Finding one. The closest I can find is 250 Ma/250V .

    I think I might have choice but to use the 250 Ma. I have literally have went to every parts and hardware store in my area. The local radio shack has closed down and the nearest one is 70 miles away. It's 25% larger in amp rating but at the same time and only 50 more Ma..
    2000 Mustang GT SOHC 4.6L : 665hp at the tirel
    11.00 @ 134 mph... A 17 year love affair...


    Wyotech Graduate 03/14 : High Performance 1 & 2...Engine Management Systems 1 & 2...Powertrain...
    Chassis/Suspension & Braking systems.. 3.7 GPA.

  6. #6
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    Default Re: Parasitic draw on battery when parked.

    Yep, been there. There used to be an electronics supply in Morgantown down on Beechurst, can't remember the name and don't know if they're still around.

    Irregardless, the 250ma fuse will likely be fine.
    JP
    Bigger, Stronger, Faster...

  7. #7
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    Default Re: Parasitic draw on battery when parked.

    Did a little looking around in Google and found this forum that might offer some help.

    http://www.allfordmustangs.com/forum...e-problem.html

  8. #8
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    Default Re: Parasitic draw on battery when parked.

    Quote Originally Posted by RGL10 View Post
    Did a little looking around in Google and found this forum that might offer some help.

    http://www.allfordmustangs.com/forum...e-problem.html
    Interesting. I replaced a body control module a few years back. On my amp meter set to ten amps it shows 0.19 is that 190 milli amps? The fuse that drops the voltage is the pcm/cluster maxi fuse. Then it goes to zero.
    2000 Mustang GT SOHC 4.6L : 665hp at the tirel
    11.00 @ 134 mph... A 17 year love affair...


    Wyotech Graduate 03/14 : High Performance 1 & 2...Engine Management Systems 1 & 2...Powertrain...
    Chassis/Suspension & Braking systems.. 3.7 GPA.

  9. #9
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    Default Re: Parasitic draw on battery when parked.

    If Im looking at the right maxifuse then that powers several fuses in the dashboard fuse box. Fuse numbers 1, 7, 13, 19, 25, 27, 33 and 39 which happens to be the fuse most Mustang owners have to pull to stop the draw. Also I believe you are right on the current reading being 190 milliamps which is at least three or four times to much. Try pulling each of those fuses one at a time with the doors closed of course to see if the draw goes down, Id start with number 39.

  10. #10
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    Default Re: Parasitic draw on battery when parked.

    Only 39 makes a difference.
    2000 Mustang GT SOHC 4.6L : 665hp at the tirel
    11.00 @ 134 mph... A 17 year love affair...


    Wyotech Graduate 03/14 : High Performance 1 & 2...Engine Management Systems 1 & 2...Powertrain...
    Chassis/Suspension & Braking systems.. 3.7 GPA.

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