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Battery Drain on Radio/dome light circuit

 
Old Mar 31, 2015, 03:03 PM
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Battery Drain on Radio/dome light circuit

Long story short, I finally tracked down that I have a 580mAh drain on my battery when the radio/dome light fuses are connected under the hood these are the two fuses that have the yellow connecting bracket on them. Not sure why its there but, whatever...

So I unplugged my radio, still has a draw, so I know its not that..
My dome lights have been acting weird ever since I got the car, they will not come on some times, when they dont I jiggle the door sensor but they never come on. So I don't think it's that..

I know there is something that makes the lights dim after a certain time the doors are shut, could this be drawing current all the time??
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Old Apr 2, 2015, 11:49 AM
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It only gets weirder.
When I have these fuses pulled, I can't use my key FOB, and the locks will still lock via the button.. However if I turn the car off and the fuses are pulled, they will not lock with the button.

Last edited by cerevo; Apr 2, 2015 at 01:15 PM.
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Old Jul 2, 2015, 09:29 AM
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So I got to looking into this a bit more, looks like there is something in the FSM that Mitsubishi calls the SWS (Simplified Wiring System) which to me looks like a secondary ECU for the electrical stuff. Supposedly this controls the autodown button for the power window, the auto open for the sun roof, the keyless entry, the dome light dimmer, etc.

I'm wondering if this thing has gone bad in my car and is what's causing my battery drain. Now I just need to find it. I assume it's up under the dashboard... Anyone ever dealt with this thing before?
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Old Oct 4, 2015, 07:44 AM
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just a small update, I pulled the SWS "front ECU" in the fuse box under the hood and it still had the drain on the circuit..
I think it may be the driver door lock. It no longer works (hasn't for a good while) and I suspect maybe its shorting out or something and causing the drain. I will try to unplug that and see if I still have parasitic drain.
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Old Oct 11, 2015, 12:13 PM
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When troubleshooting a drain such as this I always put my ammeter directly on the battery. Make sure nobody turns the key to the crank position or you'll blow your meters fuse. Most meters with an amp setting will measure up to 10A wired in series with a circuit so you should be able to turn the key on, just not to crank.

I would pull fuses one at a time until I find the drain and find the issue from there. You've already narrowed it down to one of two fuses. I would pull each fuse one at time to see which of them the drain is really on. Did you already do that? Wasn't certain from your description.

Once you are down to the one fuse, I would go through the electrical drawings and find each item on that circuit and check each one by disconnecting them until you eliminate the drain.

Note that some devices will draw some power for a short period of time after the key is removed and some for a period of time after you get out of the car and close the door. Make sure you monitor the amperage for at least 5-10 minutes after you have everything off and all the doors are closed. Needs to be in a stable "dormant" state to make sure there really is an issue.
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Old Oct 12, 2015, 07:07 AM
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Yeah that's what I had done down to the point of one of the two circuits but I didn't know how to get those fuses out at the time. I just haven't had time to narrow it down from there yet since I moved.

I also had my ammeter hooked up for over 30 minutes while doing that and it always read the 580 mah. The car hadn't been turned on in over a week, I hooked up my meter and everything but the trunk was closed (battery is in the trunk)

I really think it's the door lock though. Its been going bad ever since I got the car and will not even lock now.
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Old Oct 12, 2015, 07:24 AM
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#1 no lights at all or anything should be on when tracking down draw on a battery. it's going to give you false alarms. unplug any trunk lights. clamp down any door open sensors

you want that car's ecu / whatever manages it to be able to go to sleep after ~30 seconds (varies by car) so that the draw goes down to the idle 15-30ma draw that most cars have
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Old Oct 12, 2015, 07:41 AM
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Another thing to look for when troubleshooting dome light/clock/radio memory issues is to check inside the cig lighter socket. I haven't checked on the Evo to confirm that it is on the same circuit but when I had my shop we fished a lot of junk out of those sockets that was blowing fuses. Coins, bits of wire, etc. Many cars have that socket on the same circuit.
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Old Oct 12, 2015, 08:08 AM
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Originally Posted by qsiguy View Post
Another thing to look for when troubleshooting dome light/clock/radio memory issues is to check inside the cig lighter socket. I haven't checked on the Evo to confirm that it is on the same circuit but when I had my shop we fished a lot of junk out of those sockets that was blowing fuses. Coins, bits of wire, etc. Many cars have that socket on the same circuit.
I believe it is on the dome light circuit. Good thought, I may look into this more when I get home today. Thanks!
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Old Feb 9, 2017, 06:24 AM
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Just want to bump this and use this to keep up with my endeavors on this issue. This has claimed the life of my Optima Yellow top (really it was probably overcharging that killed it).
Now that the engine is rebuilt and everything else is good I want to put some time into tracking down my drain. I replaced that door lock last fall and although its nice for the door to lock again, it did not cure my problem.
I will check the cigarette lighter tonight when I get home and see if a simple unplug of that fixes this and report back.
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Old Feb 22, 2017, 06:43 PM
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The hot to the lighter is a popular way to power aftermarket accessories. I've used it.

The SWS is Mitsubishi's pet name for CAN buss. "A Controller Area Network (CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles, but is also used in many other contexts." - Wikipedia

CAN buss is used to pass information concerning door locks and other activities in the vehicles. It cuts down on the number of wires that would of necessity otherwise be required. Hence Simplified Wiring System.
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Old Mar 11, 2017, 03:26 PM
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well, I'm not sure what's changed but when I set my multimeter to "10" under the Amps category, and move my lead over to the amps socket, I get 0.08 - 0.09 which I think means 80 to 90 mAH?
My other options under amps are 20m and 200m.. Am I reading it correctly?

There was nothing in the cigarette lighter socket I even took a magnet to it to see if I could get anything out.
I know I have done it once but I plan on doing it again to unplug all the aftermarket gauges and my radio. Last time the gauges and radio showed no difference in current draw. I did not think to unplug my amp though... I will try that first since that fuse is easy to get to...
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Old Mar 14, 2017, 06:58 PM
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I unplugged my amp fuse, no change, I'm just not sure what else there is to try?
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