battery drain!

motaaa · Dec 30, 2008

okay.
a few months ago my battery started draining overnight even when i would drive it consistently.
took the battery in, turns out the battery was bad. so i bought a new one and it worked great for about 2 months, then last week it started draining again since i havent been driving it as much. i took in my alternator and the test showed it passed.. so now im stumped.

visually, there is no reason for the battery to be draining like that. dome lights stay off, radio off, dash components off, i cant see anything that looks like a short. ive been reading around and think it could be a bad puter, or a bad ground.

are there any commonalities with this? if so HOW DO I FIX IT???

PetesPonies · Dec 30, 2008

You need an ammeter to measure current drain. It gets hooked in series with the battery. You'll have to unhook one cable and hook the ammeter inbetween. Then you should see the amp usage. satart pulling fuses until the drain stops. Then you have found the circuit that is teh problem. See what devices are on that circuit and start checking them out. Electrical problems are work, no short cuts.

Explorin94 · Dec 31, 2008

You can also use a test light. Put it between the negative cable and the negative post of the battery. Of course with the battery disconnected. Start pulling fuses and watch the light to see if it dims when you pull the fuse of the circuit it is on. The light should be very dim as there should be some type of parasitic load from a memory of a stereo or computer. The ammeter is more precise as to what amperage is being drawn.

fordmandan87 · Jan 1, 2009

shpuld be no more than .50milliamps drain after 45 minutes of off time

motaaa · Jan 7, 2009

okay so i tried to do that amp test but my multimeter wont read it,
i think i blew the fuse but even when i bypassed the fuse it still wouldnt read it..
what am i doing wrong?

fordmandan87 · Jan 7, 2009

have you connected the two terminals via the dmm or did you have the battary connected when you hooked them up

motaaa · Jan 7, 2009

i disconnected the neg terminal and connected one end my the meter to the gnd screw and other end to the neg terminal on the battery.
set my multimeter to DC, mA 200

1988broncoll · Jan 7, 2009

I just went through this same problem and I took my alt in and had it tested at 3 different places all said it was good because while it was turning it was charging the right amount. BUT the problem remained. I finally got p*ssed off and took the alt off of my buddies ranger that was brand new and it stopped draining.... what had happened was the bearing inside was starting to go bad and when I would bolt it up and tighten the belt it put enough strain on it to make it touch the brushes constantly and draw power..... To test it you should have 2 plugs on your alt. hook your meter to your battery to see the voltage and unhook both the plugs off of your alt and then let the truck for an hour or so and see if voltage dropped on the battery at all. I did the pulling fuse thing and all and it didnt work then I finally tried that and it was the problem. Good Luck hope you figure it out soon I racked my brain for 3 weeks before i figured it out. I was to the point where when id get to work Id pop the hood and disconnect the battery so i knew when I got done itd start after i hooked the cables back up but that got old quick

PetesPonies · Jan 13, 2009

well do you understand that measuring amperage means your ammeter is hooked in series?

sjr53 · Jan 13, 2009

You need a bigger ammeter. Start with a 10 or 20 Amp range. A failed alternator has usually been the cause for me. They can draw some amps when they fail from overloading them during a jump start.

motaaa · Jan 16, 2009

yeah i hooked it in series but still wont work.

where can i find a ammeter that strong? autozone and radioshack ammeters only go up to like 2 amps..

is there a way to test the computer?
or maybe eliminate the computer?

PetesPonies · Jan 16, 2009

well if you are drawing that many amps, then it probably is in the alternator. You could use a test light instead of the ammeter. Then you can start pullinmg fuses to see if the light goes out. Then disconnect the alt and see if it goes out. An ammeter that will measure above 10 amps, is going to cost a few bucks

sjr53 · Jan 16, 2009

Harbor Freight has a $10 digital multimeter that usually is on sale for under $3 that does 10 amps DC. I bought 4 of them and have a ccouple others that do 20 amps. Radio Shack should have one for around $20.

88broncoll · Jan 20, 2009

ive seen the alternator do it to me more times than i care to remember on a few different ford veichles, not just the b2. If you pull the plugs out of the alternator and it stops killing it, put on a new alternator. there is a diode in there that goes bad. it would charge like a trooper, work fine all day. but the next morning it would be dead. I drove it for months, opening the hood and plugging the alternator back in.

battery drain!

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