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Discussion Starter #1
Hello,

I've noticed something strange with my new-to me Bronco, if I let it sit for 4 days or so without driving it the battery dies and it needs to be recharged. I replaced the battery thinking that was the problem and I had no difficulty for about a month but today I went out to start the truck after it sat for 3 days(albeit in 10 degree temperatures) and the battery was pretty much completely drained. I know the charging system is working ok as I just drove the truck on a 8 hour each way roundtrip last week with no difficulty. Any help would be appreciated.

Thanks,
Ray
 

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Sounds like you have a short somewhere drawing down the battery.
Have you checked the battery voltage with the vehicle turned off and while running.
I had a short at the wires where the harness goes from the fender to the tailgate which ran down the battery. The wires flex here alot and after awhile and break through. Might be worth checking.
You can get free battery and alternator checks at most auto parts stores for free. Takes only a few minutes.
 

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My Bronco used to be a police vehicle so it has tons of wiring on it that's no longer connected to anything as the extra lights and equipment have been removed...I suppose if something isn't tied into the igntion relay(or whatever the proper term is for items that are powered up only when the key switch is on) and the bare wire is just hitting against metal it could be drawing enough current to slowly drain down the battery over the course of a few days huh?

There are so many random wires running all over my truck maybe I need to just make a habit ot starting and running the thing for a few minutes everyday to ensure the battery doesn't run down. I have had the battery checked at autozone and they said it came out as fine, just drawn down.
 

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Thanks a lot for the suggestion on removing the neutral cable , that will be a great temporary help while I track down where the drain is coming from. This used to be a state police vehicle with 2 batteries and it has an extra fuse panel and tons(i'd say 25+) extra fuses and wires running through it so I think it's going to take me awhile to track this drain down. I got my battery charged up at Autozone tonight so I should be good to go for work tommorow..mising it today means I'm gonna be out cruising for dollar drafts tonight and hoping the girlfriend pays for herself :)

-Ray
 

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I have the same issue. My Bronc had an old alarm system, CB wiring, and hella trailer wiring. I pulled all of it out and STILL have a drain. So I put a quick release on my cable for now until I can track it down. But tghis is a pain in th ass because my computer gets wiped out every night when I unhook the battery so it takes a while to get the idle normal in the am.
 

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Get a multimeter. Start at the solenoid comming off the batter, disconnect a wire off of it. turn on the multimeter to amps and connect one lead to the wire and the other lead where the wire was connecting. This way the juice has to flow through your multimeter & and it will measure how many amps are being drawn.

Do it with your key off. And start at the battery. I would say anything over a 1 or 2 amp draw needs to be fixed. Mind you the stereo has a small draw. Lets us know what ya find
 

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Whatever it is, it goes thru your fuse block. Put the multimeter in series between the neg on the battery and the disconnected neg cable. Then start pulling fuses 'til the drain stops. At least that narrows it down to a circuit.

If you can pull all the fuses, and it still shows a drain, it's between the fuse block and the battery. Check the back-side of the fuse holders to ground with an ohm-meter.
 

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85f150 said:
I would say anything over a 1 or 2 amp draw needs to be fixed. Mind you the stereo has a small draw. Lets us know what ya find
I would say anything over 0.1 amps and you have a problem
 

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I had the same problem. Check the battery post clamps on the cables. They get some sort of corrosion in there and just need cleaned out or replaced. It gets corroded to the point where there's no connection and while you're driving the bat. won't get any charge and will die after a few starts. Keep in mind once the truck is running the alternator will give you all the juice you need to keep the car running battery or not.
 

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marv said:
Whatever it is, it goes thru your fuse block. Put the multimeter in series between the neg on the battery and the disconnected neg cable. Then start pulling fuses 'til the drain stops. At least that narrows it down to a circuit.

If you can pull all the fuses, and it still shows a drain, it's between the fuse block and the battery. Check the back-side of the fuse holders to ground with an ohm-meter.

this is exactly what i was gonna put up on here this is the easiest way to find electrical troubles.. and i used to work on para-transit buses with miles and miles of wiring and this would help out everytime.. but alot of the time with the 200 amp altornaters when they would sit and idle thats when they would loose juice to the battery since they pull so much amperage with the lights and all.. plus the turbo diesels always had issues with grounding crap out since its so damn tight in those e350's under the hood..

i would take me 4 hours to change a serpintene blet cause youd have to pull out the radiator the intercooler and pos 3 piece fan shroud that actually bolts to the front of the block so theres no way around it..:shocked
 

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bad alternator can suck power when the motor is off.

Have the alt tested at Autozone, if they do that.
 

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raycgl said:
My Bronco used to be a police vehicle so it has tons of wiring on it that's no longer connected to anything as the extra lights and equipment have been removed...I suppose if something isn't tied into the igntion relay(or whatever the proper term is for items that are powered up only when the key switch is on) and the bare wire is just hitting against metal it could be drawing enough current to slowly drain down the battery over the course of a few days huh?

There are so many random wires running all over my truck maybe I need to just make a habit ot starting and running the thing for a few minutes everyday to ensure the battery doesn't run down. I have had the battery checked at autozone and they said it came out as fine, just drawn down.
I feel your pain brother. I had the same issues. Do exactly what marv said. Ammeter between the neg batt post and ground wire. Pull stuff one at a time. Some of mine were easy to find, smoked fuses alot.
Where are you located, what do you know about your bronco's past life?
 

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I just went through the same thing. Checked all the fuse circuits and found nothing. Pulled the alternator and had it checked. It was OK. The guy at autozone told me to change the voltage regulator and that was it.
 

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check out my posts here: http://fullsizebronco.com/forum/showthread.php?t=63631

good advice on how to track down the drain.

also for a good temp. fix you can get one of thes and install it under the hood or anywhere you wanna put it for 17.99 (could slow down a thief for a few minutes too)

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLA-87181&N=115&autoview=sku

or you can find one at just about any parts store..and probably walmart.

only problem is you'll always lose your radio presets, and i dont know your model year, but i believe you'll lose any "learned" programming within the ECU (it compensates for warn sensors etc..so it may forget the "curves" for the first couple of miles until it relearns them)
 
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