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I have diagnosed 2004 Acura TL with a multimeter a parasitic drain on my car and narrowed it down to the interior light circuit. Before I started pulling fuses to see which circuit was the culprit, when I hooked up the multimeter to the battery to see what the draw was, it registers 600 milliamps, then less than 5 seconds later, it goes down to 200-300 milliamps, stays there for about 15-20 seconds roughly, then it spikes back up to 600. I watched this occur for about 5 minutes. The pattern repeats over and over, never changing. More specifically, when it comes down from the spike, after approximately 5 seconds, it goes to approximately 300 milliamps and holds there for about 1-2 seconds, then it goes back down to around 200, then repeats the same thing, spiking about 15 seconds later to 600, etc.

I started pulling fuses under the dash and the multimeter hit 20-40 milliamps when I pulled the interior light fuse.

I checked the trunk light and it is off with the trunk closed and there are no other internal lights on in the car. any ideas of what could be causing this consistent spike in this circuit? Thanks in advance!

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  • With the fuse pulled did you monitor the meter for a period of time to see if the higher draw cycles again?
    – mikes
    Aug 17, 2019 at 22:07
  • Yep. It stayed down after fuse was pulled.
    – BILL WAGNER
    Aug 17, 2019 at 22:16
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    It is a long shot, I have seen bulb filaments break and cause a high resistance short. You can eliminate the by unplugging them one at a time.
    – mikes
    Aug 17, 2019 at 22:28
  • @mikes yeah I wish it were that easy--I timed the spikes and they are exact each and every time. Seems to me a short in a bulb wouldn't do that. Every 600 spike is 7 seconds, then it sits at approx 300 for 4 seconds, then goes down to 200 for 20 seconds and the cycle repeats at exactly the same intervals. It seems to be on a timer.
    – BILL WAGNER
    Aug 17, 2019 at 23:06
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    I've read (AAA junk mail) that an 'electronic key' stored too near a car can drain the battery. Unlikely to be on the lighting fuse, but easy to check. Also, if bought used, have you checked for other aftermarket devices? (eg, remote start?)
    – George
    Aug 18, 2019 at 10:08

1 Answer 1

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Here's the breakdown of the power distribution from Fuse #6.

You have a roof console unit, keyless receiver unit (George may be on to something), handsfree control unit, and some other gizmos which might be "smart" and cause the kind of pulsating timed loads you describe.

An active key in the vicinity might cause such a thing. The key is "waking up" the car in anticipation of being opened and/or started.

Hopefully this diagram gives you a place to start looking:

enter image description here

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