testing battery drain

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Nov 20, 2003
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How do I test battery drain? After sitting for a week my battery is dead. I have a Optima red top which is only 1 year old. The alternator has been tested and is fine.

do I put a meter between the negative terminal and the body set to amps, then start pulling fuses?

What is an acceptable draw w/o the key in the ignition?

Kelly
 
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Jul 7, 2004
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Kelly;

The way I did this was to remove the positive terminal from the battery and connect a DC ammeter from the battery + post to the terminal u just removed. The key should be off, no starting, no engine running.

The ECU is connected to the battery thru the MAIN fuse link and is on all the time; it draws around 12ma.

I have a similar problem and am leaning toward an alternator leakage problem. The alternator sits at battery voltage at all times and only its rectifier diodes prevent battery discharge.

Her is a picture diagram of how the system is wired.

http://homepage.mac.com/dfmorse/BattProj2/page9.html

...
 
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Spokane WA, USA
Have you made CERTAIN that someone did not switch one of your dome lights to the "always on" position? If not, check that first. Been there - done that!! Also, did the place that tested the alternator determine that the battery is ok? You may just have a shorted cell. If these items are ok....

Charge your battery overnight or until the charger shuts off.

Most digital multi-meters have an ammeter function. The problem is that they are usually only rated for 1 or 2 amps, and maybe as little as 300 mA. It is very easy to pop the meter's fuse if you turn on a light or open a door or just have an excessive current leak.

I suggest that if your meter is one of these with a low amp rating, you remove most of the truck's fuses, hook up the multimeter, and see what it reads. It is NOT a good idea to disconnect just the positive battery lead! You can just as easily connect the meter in series with the negative terminal and negative cable end. This will eliminate the possibility of your shorting out the plus terminal and hurting yourself.

With the key OFF, start installing fuses one at a time until the meter reading either shoots up or the meter's fuse blows ;)

That will tell you which circuit(s) are the problem. From that point on, it is a matter of disconnecting components or connectors until you have isolated the culpret. Hopefully it will be easy to figure out. Do you have a factory wiring diagram? It might be very helpful.

Good luck - problems like these can be tough to troubleshoot!


John Davies
 
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Mar 28, 2003
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I have a similar problem with my 91 cruiser. I found that the Dome fuse was the one that was adding a great deal of draw on the system. The problem with removing the Dome fuse, is that you lose a lot of stuff(radio being the most key). I have not bee able to isolate the problem down any further than that. I would be curious to see if you are having the same problem. Please post if you determine what the draw was. I took it to a shop a month ago, and they said that I was getting about 75 miliAmp's of draw on the battery. They thought it was high, but not crazy high. I did have them pull out the after market alarm, which I had a concern was causing the problem. Unfortunately I did not have them do the draw reading before they pulled it out, so I'm not sure if that helped the situation or not.

Take care.
Sony
 

Gumby

Supamod
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I use a test light between the negative terminal and the negative cable end. If it lights the light, it's enough to be a problem.

If you let it sit for a week at a time, you should get a battery tender on it. Even one of the solar ones that sit in your window work pretty good.

Red tops do not like total discharge and recharges.
 
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Nov 20, 2003
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Well I tested it this weekend, I have a 300ma draw, obviously enough to flaten the battery, now to determine what is causing this. I didn't have time to start pulling fuses since it was getting to dark. I'm going to attempt again this weekend.

Kelly
 
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EVERGREEN, CO, USA
Great Kelly;

U do have a wiring diagram, right? The EWD for 1991 will probably have a "Current Flow Chart" inside the manual. If u remove one of the fuse links [say, AM1] while ur measuring the 0.3 amp drain; u may see a change in the ammeter; keep doing this with each fuse link and it may be possible to isolate drain to one fuse link. Then, look at the chart to determine the possible circuits effected.

Keep us posted

...
 
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Nov 20, 2003
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Yep, I've got the FSM. I jsut need some dry weather to work on this.
 
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spfrancis said:
I have a similar problem with my 91 cruiser. I found that the Dome fuse was the one that was adding a great deal of draw on the system. The problem with removing the Dome fuse, is that you lose a lot of stuff(radio being the most key). I have not bee able to isolate the problem down any further than that. I would be curious to see if you are having the same problem. Please post if you determine what the draw was. I took it to a shop a month ago, and they said that I was getting about 75 miliAmp's of draw on the battery. They thought it was high, but not crazy high. I did have them pull out the after market alarm, which I had a concern was causing the problem. Unfortunately I did not have them do the draw reading before they pulled it out, so I'm not sure if that helped the situation or not.

Take care.
Sony
I adjusted the door switches (driver and frnt passenger) disconnected the door courtesy lights just unpluged them and the drain went from 80mA to 25mA
 
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Nov 20, 2003
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It looks like my Alpine alarm was drawing all the current after 14 years of service it died.

I now have 15.56 ma draw, is this acceptable? I searched the FSM and owners manual and I cannot find what an acceptable amount is.
 
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marshalltown iowa
mine drains too,

i disconnect battery and use battery maintainer to keep charged
 

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