TahoeTaco

I've been having problems with my battery lately, if the car sits very long (overnight) the battery goes dead. The alternator is working ( I measure about 14.5 volts at the battery with the engine running). I tried testing for parasitic drain, unhooked the neg. bat cable, and using a multimeter between the neg batt post and the neg bat cable I measure 12.3 volts, with all lights and accesories off. I pulled all the fuses and nothing made that number drop. It seems to me that number is very high, and there is obviously a short somewhere but I dont know how to find it. I disconected the pos. battery cable from the starter thinking that was it, but it didnt make a difference.
Any help would be great

I have a 91 4runner 22re with no mods

AH64ID

I dont understand the hooking of the multi meter to the neg cable and post?? Neg to Neg should not show any volts... Maybe its somthing new to me.. can you explain?

Has the battery been allowed to die from something else, maybe dome light, etc? Once a battery dies its not any good any more, usually depending on type.

TahoeTaco

The idea is that if something is drawing power from the battery with engine and everyting off it will show up if you hook up a multimeter or test light inline between the neg post and cable.
The battery has gone dead a couple of times, but if I charge it back up it holds the charge as long as leave the battery unhooked. As soon as I reconnect the battery up it starts draining. So I think the battery is still good, but something caused it to go dead, I never left headlights on ect. it was just random.

Elton

how old is the battery ?

TahoeTaco

its about a year old, its an optima red top.
I also replaced the pos batt cable a few months ago, but the neg cable is pretty old, could that be the problem?

AH64ID

I dont think that theory is sound. If you hook up to the neg cable and the neg post you will have no way of measuring voltage, I cant even figure out how you have a voltage reading doing that as you are not reading the + side anywhere.. doesnt make electrical sence. A test light wont light for the same reason, you only have a ground no +.

The way to tell if you have a draw with everything off is with an ammeter, not a voltmeter. Volts indicate battery health, amps indicate load.

From what I have read if a red top goes dead its done....

It is possible you have something draining the battery but I also think its a good possibility your battery is shot.

fireteacher

load test it at autozone for free and eliminate the possibility

HAVOC

AH64 is correct. Black lead on meter goes to the NEG. battery terminal. Red lead on meter goes to the NEG battery cable. POS. side of battery stays connected.
Set the meter to read mA (milliamps). Make sure the doors are shut and the key is out of the vehicle. Then wait for the meter to stop moving (the computers going to "sleep") (it takes longer with new cars and the number of computers in them).
Then start pulling fuses (start under the hood), pull the fuse, then put it back in place. Then pull the fuses in the cab (DO NOT OPEN THE DOOR! that's a quick way to blow the fuse in the meter). Once you find a big drop on the meter, that should tell you where to look for the draw.

runethechamp

Remember, there's going to small current draw with everything off. I went through the same thing a little while ago, and I think it is the fuse for interior stuff that draws a few miliamps to cover the clock and radio memory. In my case it turned out to be just a dead battery.

See this post: https://www.yotatech.com/forums/f2/battery-electricity-question-69604/

HAVOC

Yeah, the draw will always be there, but just a small amount. I don't think that it's a specification that you'll find in a Haynes/Chilton or FSM.