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Unknown drain on battery

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#1 football_coach


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Posted 17 September 2017 - 01:40 PM

I've had to jump start my 2003 Lincoln LS 3.9 several times. I replaced the battery which now I think I didn't need to. Battery still dead. There is a mechanic at the school bus garage who looked at it and said the glove box light was staying on. He disconnected it. Problem solved . . I thought. That was about 3 weeks ago. This morning the battery is dead again. I opened the trunk and heard a clicking noise coming from the little contol box beside the battery. When I connected jumper cables to it the clicking stopped. Why? What was causing the clicking noise and what could be draining my battery? Thanks.

#2 Karrpilot



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Posted 17 September 2017 - 03:38 PM

Ford uses what is commonly called battery saver relays. What they do and how they work is as follows. They are supposed to shut off power to whatever they are controlling after X amount of time. So say you leave your headlights on. The relay that controls that circuit may be programmed to shut off the lights after 15 minutes of time goes by. To save you from a dead battery.


If that relay sticks, or whatever is controlling it fails, the headlights won't shut off, and you will end up with a dead battery. Ford also might use that same system for an ABS or airbag module. So that again, after X amount of time, the module can go to sleep, still retain it's memory functions, and spit out any trouble codes in memory when and if called upon.


Trying to chase this issue down is a huge pain in the backsides. Because you would need to install a meter inline with a battery cable, wait at least an hour for the module(s) to go to sleep, and then start the investigations. I think the Ford specifications regarding battery drain is no more than 50 mili amps. I have seen everything from radio amps to the smart junction box itself not going into sleep mode, and killing batteries.


A cheap alternative is if the vehicle can not be driven every day, or if it sees low mileage, is a battery tender. It supplies a 1/2 amp of charge into the battery, and shuts off / cycles itself when the battery becomes fully charged. The key is to always plug it in when the vehicle is shut off for the night. What I do to remind me to unplug it before driving off is this: Wrap the power cord around the drivers side mirror. Then of course one does have to remember to plug it back in daily. Kind of like what we do with our diesel block heaters in the winter. After a while, it becomes 2nd nature.

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#3 Mike N

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Posted 17 September 2017 - 04:48 PM

Are there any aftermarket accessories installed on the car, like an alarm or remote start? That's usually the first place I look for a parasitic draw.

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#4 football_coach


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Posted 18 September 2017 - 10:56 PM

No aftermarket accessories except for a dashcam which I disconnected. However, the advancetrak, ABS, and brake system warning lights are all on. Also, I noticed the light on the traction control switch on the center console is burning (orange) when the motor is off. The light goes off when I start the car. I hadn't driven the car for a couple of days before I tried to start it and the battery was dead. I won't have an opportunity to take it to a mechanic for a couple of weeks. I drive 90 miles round trip on the Interstate 6 days a week plus short trips locally.

#5 ok44


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Posted 19 September 2017 - 02:23 PM

With the mountain of wiring, relays, control modules, etc on modern cars it would be near impossible to track this down without a proper wiring manual.


This would mean a Helm manual. Those are available from Helm, Inc. or possibly found on eBay on the cheap. They really clear up some of the murkiness involving wiring although one should be warned that finding the answer to this problem could still be time consuming.


With any late model Ford I've ever owned my first step has always been to buy the Helm manual for that particular car. Helm manuals are also used by Ford dealers.

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