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Can't locate parasitic draw
Posted: Sat Mar 28, 2020 10:10 am
by Avittery
Ever since I have owned my L400 it has had a parasitic drain that draws about 280 mAmps. There is a battery switch that I have to constantly use to prevent a dead battery.
I've tested every fuse inside underneath the steering wheel, and under the hood and couldn't find anything.
Does anyone have any suggestions of where else to test? Thanks!
Can't locate parasitic draw
Posted: Sat Mar 28, 2020 2:03 pm
by deskinthewoods
I just went through this on my L300.
No fuses pulled showed any difference but I also checked the fusible links, which I’d assume you may also have. A set of wires by the battery, hooked in on the positive side. Maybe 3 or 4 of them. Pull each of those.
Although one of mine did stop the drain I still couldn’t find the grounded wire in the loom.
I accidentally stumbled on the culprit though. The main connection at the alternator. The rubber protective cover had split and the wire was grounding on the alternator body. I taped it up and repositioned so it wasn’t touching.
Long story. Check the alternator.
Can't locate parasitic draw
Posted: Sat Mar 28, 2020 5:17 pm
by DeliTan2
For me it was my crappy Chinese stereo
john
Can't locate parasitic draw
Posted: Sun Mar 29, 2020 10:27 am
by sck_nogas
What I had to do to find my parasitic draw in my L300, was think outside the box. :)
1 - Connect my battery to a trickle charger
2 - Let the car sit overnight
3 - Use a
FLIR One Gen3 iPhone adapter (about $200) to look at the temperature of things in the car
4 - Nothing under the dash was warm (around 64F)
5 - Nothing in the battery box was warm (except the battery)
6 - The engine was cold (around 68F)
7 - The turbo and exhaust were warm (but that seemed reasonalble at 78F)
8 - The alternator was GLOWING at 110F
Turns out I had a bad diode. The previous owner and their mechanics had just put on a quick battery disconnect and forgot about it, but that would drive me crazy!
The FLIR is useful for finding insulation issues in homes, cold drafts, Water leaks (due to moisture being cooler), and now electrical issues. :D
Can't locate parasitic draw
Posted: Mon Mar 30, 2020 9:25 am
by Avittery
Well I narrowed it down to the alternator fusible link and tested the diode on my alternator and it's totally fine! the draw is still there even with the alternator completely disconnected. There must be a bad diode somewhere between the alternator and the battery.