How do I check a battery drain?
Thread Starter
Pro
Joined: May 2005
Posts: 592
Likes: 1
From: Shreveport Louisiana LSU
How do I check a battery drain?
If the 81 sits over a week or so, the battery is dead. How do I check to see if there is a drain or whether the battery is history. I have a multi meter, so can I disconnect a battery cable, set the meter on amps and put the leads on the battery post and the cable end to see if there is an amp showing? Or, do I just put a switch on the battery and forget it?
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
You're better off to determine what is the actual problem before deciding to simply use a cut-off switch. In the end you may do that but the problem could be simple and easily remedied. You may even have a bad battery.
Take your multi-meter (or even a test light), remove a battery cable (I think negative is best as it's less likely to create a spark) and see what the draw is (or if a test light, it illuminates).
Then start removing and replacing fuses one at a time, and see if the amperage drain drops (or test light goes out). Once you do that, you should be able to isolate which circuit is causing the draw.
Once you've isolated the circuit, you can concentrate on finding the exact cause. It could be in the light circuit, a bad alternator, any number of places, but it should be not too difficult to find once you have the circuit identified.
Take your multi-meter (or even a test light), remove a battery cable (I think negative is best as it's less likely to create a spark) and see what the draw is (or if a test light, it illuminates).
Then start removing and replacing fuses one at a time, and see if the amperage drain drops (or test light goes out). Once you do that, you should be able to isolate which circuit is causing the draw.
Once you've isolated the circuit, you can concentrate on finding the exact cause. It could be in the light circuit, a bad alternator, any number of places, but it should be not too difficult to find once you have the circuit identified.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
your clock, your radio presets if electronic, your computer, your radar detector, all will draw a small amount of current while sitting...
the 1st thing you should do is go aout and get you the biggest, baddest battery with the most cranking amps you can find.. this is probably the problem... a 1 week drain will be a slow drain and hard to find..
if it was a short to ground or a dome light stuck on your battery would be dead in a day, not a week. plus a short will either blow a fuse or fusable link, or cause a fire...
my car draws 15 milliamps just sitting for the clock and radio... when I open the door, it draws 1700 milliamps.. i left my door open overnight once and my brand new 1000 amp battery was dead overnight... but it has in the past sat for 3 weeks before and atarted right up..
replace your battery...
the 1st thing you should do is go aout and get you the biggest, baddest battery with the most cranking amps you can find.. this is probably the problem... a 1 week drain will be a slow drain and hard to find..
if it was a short to ground or a dome light stuck on your battery would be dead in a day, not a week. plus a short will either blow a fuse or fusable link, or cause a fire...
my car draws 15 milliamps just sitting for the clock and radio... when I open the door, it draws 1700 milliamps.. i left my door open overnight once and my brand new 1000 amp battery was dead overnight... but it has in the past sat for 3 weeks before and atarted right up..
replace your battery...
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
Most of the generic auto parts places can test batteries and alternators. How old is the battery?
Do you have a vanity light in the visor? Check to ensure the light isn't staying on. Sounds like a no-brainer, but I've seen it happen.
Do you have a vanity light in the visor? Check to ensure the light isn't staying on. Sounds like a no-brainer, but I've seen it happen.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Good concepts above: First, determine the amount of the battery drain..make sure that your interior lights/jamb switches are "closed" so they don't confuse the issue when you check. Start on the 10A. scale on the multimeter; then, if the draw is low, you can switch over to milliamps scale for more accurate measurement.
If you have more than 100-200 milliamp draw, then you have an unwanted drain somewhere. From you description, I'm guessing you have .5 amp or more drain continuously.
Set up your meter so you can see it when you are down by the fuse block. Connect it in series with the battery so you can monitor the drain. Pull fuses...one at a time...until you find the offending circuit. Then go to the wiring diagram to identify the wiring areas which could be affected. At this point, you can use two different strategies: disconnect specific items (lights/radio/etc) one-at-a-time; or sever the circuit at different points to narrow the focus. The latter is more precise, as it will also include wiring that is not within any specific device.
With a little work and patience, you can find any electrical "drain" fairly quickly with this approach. Good luck.
If you have more than 100-200 milliamp draw, then you have an unwanted drain somewhere. From you description, I'm guessing you have .5 amp or more drain continuously.
Set up your meter so you can see it when you are down by the fuse block. Connect it in series with the battery so you can monitor the drain. Pull fuses...one at a time...until you find the offending circuit. Then go to the wiring diagram to identify the wiring areas which could be affected. At this point, you can use two different strategies: disconnect specific items (lights/radio/etc) one-at-a-time; or sever the circuit at different points to narrow the focus. The latter is more precise, as it will also include wiring that is not within any specific device.
With a little work and patience, you can find any electrical "drain" fairly quickly with this approach. Good luck.
Thread Starter
Pro
Joined: May 2005
Posts: 592
Likes: 1
From: Shreveport Louisiana LSU
With just the courtesy lights on the draw is 2.5. When they time out, the draw is .02. I haven't pulled fuses yet. There is an old viper alarm on the car. It is not functional as far as I know but there is a keypad that has a red light blinking. Also there is an electronic gadget in the back with two little lights. It seems as if these light up when I shake the car.
Burning Brakes
Joined: Jan 2009
Posts: 1,224
Likes: 1
From: Clarksville Indiana
All good advice above, my Techs in my shops do these things all the time. I dont know how "quick&easy" it will be for ya but I would like to suggest one other thing. The "wiggle" test.. Its just what it says, while watching your meter, grab different area's of wireing harness, plugs, switches, ect. and lightly tug and move them a little <wiggle> and watch for readings to bounce around.. It can help sometimes.. I also agree, FIX IT, dont switch it or get a bigger battery to run down slower.. good luck
Thread Starter
Pro
Joined: May 2005
Posts: 592
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From: Shreveport Louisiana LSU
Well, surprise, surprise. I have pliers holding in the door switch, pull every fuse, find nothing, the pliers slip and I push back in and an alarm goes off. First time ever. Now I need to trace down and disable the alarm (since I don't know the code etc). the box with the red and green leds seems to randomly change colors. I don't know if it is a motion sensor or what. Anyway, still have the amp draw.
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Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
With just the courtesy lights on the draw is 2.5. When they time out, the draw is .02. I haven't pulled fuses yet. There is an old viper alarm on the car. It is not functional as far as I know but there is a keypad that has a red light blinking. Also there is an electronic gadget in the back with two little lights. It seems as if these light up when I shake the car.
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
With just the courtesy lights on the draw is 2.5. When they time out, the draw is .02. I haven't pulled fuses yet. There is an old viper alarm on the car. It is not functional as far as I know but there is a keypad that has a red light blinking. Also there is an electronic gadget in the back with two little lights. It seems as if these light up when I shake the car.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You just have to make sure you get rid of all the offending wiring, AND repair any breaks placed in existing wiring when the alarm system was wired up. {Usually the control box takes care of breaking the circuit, but sometimes the ignition circuit is rewired, as well.}
Thread Starter
Pro
Joined: May 2005
Posts: 592
Likes: 1
From: Shreveport Louisiana LSU
Thanks for the help. I will sheetcan the alarm as soon as I can get it to a tech. I can't find much help on line other than take it out without screwing up! Restore all wiring to original. This is an outdated system and will be trashed. .03 isn't too bad on drain, the battery is 2 years old according to the code. I'll take it out and have it checked. Anyway thanks!!!!