Working around an intermittent draw

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Friend of mine has been dealing with an intermittent draw. He's had this car (2009 Crown Victoria, ex-police) to several of the best automotive electrical shops in the area, to no avail. The problem he has is that every week or so, the car will kill its battery overnight. What's made this problem especially difficult to trace is that it only exists on those nights. If you don't know which night it's going to do it, there's no way to trace it.

I gave it a go on a few different nights, but never caught it in the act. The primary suspect is the "Lighting Control Module", but that has never been verified.

The best recommendation he was given was to attempt replacing the LCM and then basically just see what happened. He's already purchased a new battery for absolutely no good reason and was not ready to try shotgunning any more parts out of little but hope.

He again visited some more shops experienced in electrical, and even a shop that only fixes Crown Victorias, and no resolution. At this point, he was desperate. He was ready to get rid of the car, rather than continue to deal with these issues. He needed a permanent solution, fast. I had only one idea:





What I did here was to route all of the battery grounds through an 80 amp continuous duty solenoid. The solenoid is fed power by a small rocker switch under his dashboard. By controlling the ground of the battery, rather than the positive circuit, I only needed to run one wire from the dash to the solenoid. The switch is still able to access power from the car's power circuit. But since the ground is cut off to everything else, only the grounded solenoid can make use of the vehicle's power system.

When he parks for long period of time, he turns off the rocker switch, and power is cut off to the whole car. When he goes to drive, he turns the switch on, engaging ground for the entire vehicle and allowing him to drive it.

This is obviously not even remotely as good as finding the true problem and correcting it, but he has 3 children he needs to move around during the day and was out of time, money, and patience. Not a perfect solution, but a solution none the less.

He made sure to toss a 1/2" wrench in the glove compartment so he can join all the grounds on the same post, should there be a failure of the solenoid, switch, or wiring. He can continue to start and drive until a repair of this new system can be performed.
 
Does this car have an entry touch pad on the door? If it does that would be a good place to look.
Moisture gets in and trips the interior lights on for a time then they go out.
I had a Ford that did this, I couldn't find the intermittent problem until one night after it rained I saw it lit up at 3am.
 
Originally Posted By: DrRoughneck
That black connector on the post is weird. You want bare metal for best conductivity, no paint.


I do think those are bare under the post, but OP will need to verify.

Good idea OP.

Really this requires pulling a LOT of fuses a LOT of times until the scheme that causes it is found. That's a lot of work...
 
Originally Posted By: JHZR2
Originally Posted By: DrRoughneck
That black connector on the post is weird. You want bare metal for best conductivity, no paint.

I do think those are bare under the post, but OP will need to verify.


Correct...

red and black "marine" terminals are NOT painted on the interior that mates with the battery post.
 
Yes, the terminal is bare under the post.

This is not a model that has a touch pad, and the interior lighting has never been observed to be on when it shouldn't.

I did initially ask him if he would like to use a more discreet switch for anti-theft purposes, but this car already has that foot operated airbag that locks the shifter from being operated unless you know where to find the bag.
 
No light for the mirror. Don't even think it has any in the visors.

The other potential problem is the remnants of the police electrical. Don't know if that may play a role as well.
 
Originally Posted By: DoubleWasp

This is obviously not even remotely as good as finding the true problem and correcting it, but...


...it is better. If you found the true problem and corrected it, the car could come up with a work around in the shape of a new mysterious power drain.

No electricity = no electrical problem. Get around that, you ******!

I disconnect the battery at the earth, but that's obviously a bit cruder. I'd have assumed this might give some memory loss problems with a newish car, but I only know about newish cars through heresay.
 
Crown Victoria seems to suffer no issues as a result, other than the clock needing to be reset.

If this were a BMW, Audi, or something, I have no doubt it would implode on itself like the house in Poltergeist.
 
Originally Posted By: DoubleWasp
Crown Victoria seems to suffer no issues as a result, other than the clock needing to be reset.

If this were a BMW, Audi, or something, I have no doubt it would implode on itself like the house in Poltergeist.


My god I couldnt imagine the lights and noises a BMW would make after waking that thing up with the cutoff switch. There would be tons of lights left on the dash.
 
When I had this exact problem with a Ford Taurus, it turned out to be a bad driver's door switch.

I only figured it out when I got up in the middle of the night for some reason, and the interior dome light was on.

I instructed the dealer to replace it, they said "we tested it and there's nothing wrong" and I said "replace it anyway."

Problem solved.
 
I had this exact intermittent draw problem with a car I had (2005 Renault Megane).

I ended up wiring a battery cut knob accessible on the front bumper. Problem solved, but I then figured out that if I cut power for a couple of seconds and put back, then leave, no draw. Go figure. ECU or Body Controller was supposedly wrong.
 
Clever solution. Any chance there is a problem with the trunk illumination light. I had that problem on an old Civic.

Also, could the owner try using a battery tender on the car to prevent the discharge from happening, although your way is just as good.
 
From tracking a similar short in a constant power circuit on my last BMW. I feel your pain. Intermittents are the pits. Heck, I knew which fuse, I had factory wiring diagrams. Trouble shooting is a logical process of elimination. Without luck, it can be a long process. The tip about a wet door opener, plus what happens overnight?.. dew Good one, Trav. How many times has that LF door been cycled? I was suspecting a trouble from the police equip de-install ..ripout. Meantime the work-around keeps the car reliable. A cheap stick on quartz clock and mebbe a 9v rigged on the back side of the solenoid to power the presets when the battery is off ??
 
Thought about tossing a spare MC battery on the backside (like a Benz), but I figured it would just get leveled like it was doing to the main battery.

The battery tender is a good idea, but he sometimes overnights with the kids at the in-laws or his mother's. Street parking. Like's to road trip alot too. Then, he'd be stuck.
 
Originally Posted By: SHOZ
Solid State modules will frequently fail in the on "position".


A thermal camera can be used to identify which module is drawing power. It'll be warmer.
 
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