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Massive battery drain

 
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Drez
Bfix "What's a Bronco?"
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Joined: 23 Mar 2014
Posts: 6

PostPosted: Sun Mar 23, 2014 2:54 pm    Post subject: Massive battery drain Reply with quote

I just picked up a 75 Bronco and I am about as good with electrical issues as my 7 year old daughter so I need some help. I am getting MASSIVE battery drain (two brand new batteries gone within two weeks), and actually seeing burn marks in the bolt holding the positive cable to the battery.

I bought a multimeter and disconnected positive wire (just read I should have pulled ground for safety, but results should be same?). I then connected multimeter to positive terminal and red wire and pulled about 13 volts. I then pulled each fuse one at a time from the glove box fuse box and there was no change in the multimeter for any of the fuses.

No idea where to go next? Could it be starter solenoid? Alternator?
Thanks in advance.
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DirtDonk
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Joined: 27 Jul 2003
Posts: 2742
Location: San Jose, CA

PostPosted: Sun Mar 23, 2014 7:19 pm    Post subject: Reply with quote

Hey Drez, welcome! Sorry to hear you're having trouble. But a couple of common areas to check. First, how long does it take to drain one? Over night? Or a few days?
And also, your testing was close, but not quite right. With either cable disconnected and the meter jumped between the contacts you will always get a "voltage" reading of battery voltage. What you need to do is set your meter for "amps" if it has that setting. That's why some prefer to use a test light instead of a meter, but the meter is still more versatile.

Do the same thing with the meter in amps (not miliamps though, as this kind of drain is way more than miliamps) and see if pulling any fuses does the trick.
If none of the fuses does the trick, don't despair, there are a couple more "thingies" that can pull power when faulty. Next disconnect the plug on the voltage regulator. Your '75 might have it on the firewall behind the air cleaner on the passenger side, or on the inner fender well/wheel house near the battery. If you're not sure what one is or looks like, it'll be a roughly 3"x3" box in either silver or blue color. They vary in height between about 2" tall for an old original type, to about 1" tall for a newer I.C. type.
Pull that plug and see if it stops the drain.

Next is the alternator. If the diode array goes bad internally it can draw power. Disconnect the alternator charge wire from the main "BAT" or "CHG" stud on the back (stock alternator) and see if that fixes it.

Also, any way you can shoot us some pics of your engine compartment? That way we can see if it's relatively stock-ish still, or has been modified. And we can see what type of alternator is in there, since that's a common part to upgrade these days.

Good luck.

Paul

_________________
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM Mr. Green
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Drez
Bfix "What's a Bronco?"
Bfix


Joined: 23 Mar 2014
Posts: 6

PostPosted: Mon Mar 24, 2014 4:09 am    Post subject: Reply with quote

Thanks for the great info! I had bought the cheapest multimeter and only has volts and ohm's, so I'll be returning for one that has amps today and hopefully get to it tonight or tomorrow night.

The drain is happening in a matter of days. However, yesterday, I had the brand new battery in and went to get gas. It barely started after fill up so I came home. I popped the hood and there was further charring on the positive terminal.

On a side note (or related?) last night I noticed the driver side headlight is about half as bright as the passenger side. I assume this would have to be a grounding issue? Could that be my issue for the battery drain?
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oldwinghunter
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PostPosted: Mon Mar 24, 2014 7:47 am    Post subject: Reply with quote

in my opinion, if there is enough of a short on the system, to cause charring at the battery post or cable, do not drive the rig... until you have gotten it figured out . basicly the battery is a hydrogen bomb... and if it has a direct short of that magnitude, you could be in big trouble, also could cause the truck to burn to the ground.
make sure that the starter is not staying engaged after starting , due to the starter solenoid sticking .
remove the ground cable , while sitting over night . until you get it all figured out .

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Drez
Bfix "What's a Bronco?"
Bfix


Joined: 23 Mar 2014
Posts: 6

PostPosted: Mon Mar 24, 2014 9:49 am    Post subject: Reply with quote

Thanks oldwinghunter - I've got it disconnected and she is stuck in the garage until I get it fixed.
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DirtDonk
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Location: San Jose, CA

PostPosted: Mon Mar 24, 2014 9:30 pm    Post subject: Reply with quote

Grounding issues abound in these things. They were just adequate when new, but add 40+ years of rust, sitting, paint, and just general panel separation anxiety and you get the picture.
The headlights are a perfect example. They're grounded to the radiator core support right there behind where they mount. But the spot-welded joints between the core support and the fender side skirts are tenuous at best sometimes.
Of course, it could be a connection or simply a failing incandescent lamp too, but one quick way to find out is to run a temporary (temporary unless it works that is) jumper wire between the ground wires/studs on the back of the panel directly to the battery negative terminal. If the lights get brighter, you know you're on to something. If not, they're you're on to Plan-B instead.

For the charring, maybe a pic would help, but either way it sounds like too much load is being pulled through the wires from some source, OR, and even more likely, the cables and/or terminals themselves are either failing, or simply under-rated for the job.
Do the battery cables look new(ish) or old? Large(ish) or small?

Good luck. Smart move to park it.

Paul

_________________
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM Mr. Green
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Drez
Bfix "What's a Bronco?"
Bfix


Joined: 23 Mar 2014
Posts: 6

PostPosted: Sun Mar 30, 2014 9:18 am    Post subject: Reply with quote

Thanks DirtDonk.

I just got back on the Bronco. It looks like it was the horn relay. I went through all fuses and alternator and nothing stopped the draw. Bbefore I tried the voltage regulator I randomly pulled the horn relay wires and that stopped the draw. I popped the relay open and the inside was rust, corrosion, and charring. I have no horn relay as of now (nothing in stock at NAPA), but there is no draw on the battery.

I changed headlights from passenger to driver to see if it was the bulb. Driver side still dim. I pulled the ground wire and cleaned the ends as well as cleaned the terminals. Hooked back up and it's almost back to new. Probably running 90% or so.
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DirtDonk
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Joined: 27 Jul 2003
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Location: San Jose, CA

PostPosted: Sun Mar 30, 2014 10:16 pm    Post subject: Reply with quote

Fantastic news!
Here is a new stock relay for the horn if you can't find one somewhere.
http://www.wildhorses4x4.com/category/s?keyword=relay

Also showing are the headlight relay kits (I like the cheaper one myself) that would improve the brightness of your setup. It won't help a bad ground, but if the ground is now good, your lack of brightness is probably coming from (like most of our EB's) the 40 year old wiring that was barely adequate when it was new.

Paul

_________________
'71 Bronco - 302 4v
3.5" WH/Skyjacker Lift
33 x 11.50 x15 Thornbirds on 15x7 Enkei's
Kayline soft top
Hanson bumpers
Dual batteries, Large 1G alt.

WWW.WILDHORSES4X4.COM Mr. Green
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Stan
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Joined: 29 Jun 2004
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Location: Boring Or

PostPosted: Tue Apr 01, 2014 7:27 am    Post subject: Reply with quote

Something else you should check while you have the battery cables off is the cable connector to battery terminal fit. 3-4months ago we ran into a WTH situation. The + battery connector was loose as in not tightened down - melted the connector and chared the mating surfaces - No power untill we cleaned the inside of the connector { actuall replaced it } and then cleaned the battery terminal - but the battery was ok and it started right up.
Stan

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Homer - " Facts are meaningless . You could use facts to prove anything that's even remotely true."
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Brandon
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Joined: 09 Jan 2002
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Location: USA, Australia, Bahamas, Mexico, New Zealand, & Sandy Oregon

PostPosted: Tue Apr 01, 2014 7:36 pm    Post subject: Reply with quote

Stan wrote:
Something else you should check while you have the battery cables off is the cable connector to battery terminal fit. 3-4months ago we ran into a WTH situation. The + battery connector was loose as in not tightened down - melted the connector and chared the mating surfaces - No power untill we cleaned the inside of the connector { actuall replaced it } and then cleaned the battery terminal - but the battery was ok and it started right up.
Stan


I remember this well Razz

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