OK - I have a FJ40 1974 all stock 6 cyl. It sat for about 2 weeks with an old battery and that was that - no juice and could not take a charge. I bought a new battery - gave it a charge for about 45 min on a charger and it started with no problems. I parked it for three days and the battery is dead again. (Now on charger out of FJ). Did I just not charge it enough or is there a ground somewhere - and if so - how do I trac ethat down? As always - duh and thanks.
Dead Battery
- Thread starter mattcobb
- Start date
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you should not have to charge it in the first place if its a new battery, take it back.
and yes something is sucking the juice when its off.
get a tester and start somewhere.
and yes something is sucking the juice when its off.
get a tester and start somewhere.
Obviously it is not a fast drain. A slow drain will kill a battary given enough time.
Take off the negative terminal from the battery and using a voltmeter see if you have a potential from the cable to the battary. A 12v potential means that current is flowing, you just don't know how much.
If you have a potential, start pulling fuses one at a time to see if the drain stops. If it does, then at least you've isolated it to one circuit.
If you find the circuit, you're almost home free.
One time i had a diode go out on the rectifier assembly in the alternator (a Datsun
) took forever for me to find it, and even longer to track down a replacement diode (I was a poor college kid that couldn't afford a new alt). Costs less than a couple bucks for the diode.
Good luck.
Take off the negative terminal from the battery and using a voltmeter see if you have a potential from the cable to the battary. A 12v potential means that current is flowing, you just don't know how much.
If you have a potential, start pulling fuses one at a time to see if the drain stops. If it does, then at least you've isolated it to one circuit.
If you find the circuit, you're almost home free.
One time i had a diode go out on the rectifier assembly in the alternator (a Datsun
) took forever for me to find it, and even longer to track down a replacement diode (I was a poor college kid that couldn't afford a new alt). Costs less than a couple bucks for the diode.Good luck.
- Thread starter
- #4
Thanks -
I noticed the new battery would not turn the engine so I put the charger on it - started fine - a few times then died after being parked - does the fact that I dropped in the battery and the engine carnked slow and would not start indicate anything? or just dumb bad luck?
I noticed the new battery would not turn the engine so I put the charger on it - started fine - a few times then died after being parked - does the fact that I dropped in the battery and the engine carnked slow and would not start indicate anything? or just dumb bad luck?
take it back
I should mention that if you have an LCD clock in the truck, it will pull 12v, but very little current, not enough to kill a battary. You might have to disable that before you can test each circuit.
Here is the drill:
Actually, you want to remove a battery cable and measure the current between the cable end and battery post (not voltage). Touch the cable end to the post to see if it makes a big spark first, because if the drain exceeds the rating of your meter, it might fry it. More than 50 milliamps is not good
Next start pulling fuses and look at the current drain. If you pull a particular fuse and the current drain stops, then there is a short in that circuit after the fuse.
If you pull out all the fuses and still have a drain, then the short is before the fuse block. Disconnect the B wire at the alternator and see if the drain stops. If so, there is a bad diode as mentioned above.
Actually, you want to remove a battery cable and measure the current between the cable end and battery post (not voltage). Touch the cable end to the post to see if it makes a big spark first, because if the drain exceeds the rating of your meter, it might fry it. More than 50 milliamps is not good
Next start pulling fuses and look at the current drain. If you pull a particular fuse and the current drain stops, then there is a short in that circuit after the fuse.
If you pull out all the fuses and still have a drain, then the short is before the fuse block. Disconnect the B wire at the alternator and see if the drain stops. If so, there is a bad diode as mentioned above.
I realized that, but i was afraid that someone might end up with a fried meter, most can't handle much current.
Good catch.
I'll take a stab in the dark because I don't know what type of multi-meter you have, I'm going to assume it is an analog (with a neetle).
It should probably have four places to put the probes. Put the black in the common plug, and the red in the 10A plug. Dial the selector to the 10A setting.
10A is a lot of current, so you probably won't see any movement if it is a small drain. But i'd start there, at least you are less likely to fry the meter. If you get no neetle movement, then drop it down to the milliamp setting (move the red probe and change the selector).
Do the same thing. Like Pin_Head indicated, any more than about 50miliamps is too much.
Good luck, remember, remove the negative terminal as it is safer, less likely to get a spark if you accidently short to the ground with your wrench (never done that before, not).
