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2002 Mercury sable battery keeps going dead. Bought new battery still goes dead. Will go 1 month 2 months or 1 week before going dead. 2 mechanics have checked this car and find nothing wrong with it. My husband keeps having to jump start and is getting very frustrated. My mother swears she is not leaving anything on..... HELP  

a few things.....    

there are some ways to find the problem...

there is a LOT of info i am about to give you...  and you will probably want to google... parasitic draws...

cars built since 1992 or so.. and almost every thing since 1996 have modules that have timers to keep them active until they time out and shut down...    if you disconnect the battery to check for parasitic draw.. it shuts off the modules.. when you hook up the battery again...  the draw might not show back up....

this is what professional mechanics use to find parasitic draws...  



they are available for about 130 in most parts stores if you look in their professional tool catalog that may be stashed in the back room...    aeswave had these for under 100 as i recall i would have to check the current price..  

this device clamps around wires and measures up to 60 amps...  where the larger versions that most mechanics have starts at 10 amps and reads to 400 amps...   so anything under 10 amps is just not shown ...

these also plug into a digital volt meter...  set to DC volts scale.. as they convert the amp reading to volts to be displayed..

this allows you to run the engine..    shut it off... get out    lock the door.. set the alarm...   with the hood light disconnected.. monitor the amp draw on the battery..   not just for a minute.. but for 10 minutes or even 15...   look for a MAXIMUM amp draw of 0.035 amps DC...     thats 3/10th's of an amp...  thats MAX.  most cars have 0.020 amps dc..


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you will need at least a digital volt meter with a 10 amp DC or a 15 AMP dc scale...  they can be had under 30 bucks at most stores...  harbor freight.. sears, auto parts stores... there are some models that are more expensive.. but some of the 7 buck versions will also work...

you will also need one of these...   they are also available for side post batteries..  this is like 5 bucks at HF... item 97853..



create a set of test leads... with ring terminals on the end... so you can hard wire one to the battery clamp end.. and the other to the cable end...  this allows you to  run the engine..   shut it down...  wait for the 5 or 6 minutes for all the modules to shut down...    then loosen the green knob.. so all the amp load goes through the amp meter...  this will give you a proper parasitic amp draw test....  


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years ago .. in a shop i worked at as a drivability tech...  one of the other mechanics kept having a 300ZX come back on tow trucks with totally discharged battery..       eventually we got the owner to come in with the car.. and park it just like they did at home...   they pulled up.. rolled up the windows... set the parking brake.. got out and locked the car with a key..   that was while i was looking at the amp draw with the amp clamp around the battery cables on one side..   at that point .. the amp draw went up to almost ONE amp...  seems the door lock alarm switch was shorted by the amount of car washes the car had been through...

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another thing that can be done.. is using one of these... and there are 2 different designs... one for the tiny fuses which i think this is.. and one for conventional ATO/atc fuses..




you can plug them into the fuse block one position at a time...  start the car and shut it down...  watch the amp draw of each circuit...

you could also use one of these with some wires on the end to attach to the green knob device...  to monitor the after shut down draw...    theses are under 15 bucks at HF...  

i have a 1993 olsmobile 98 elite and the battery keeps going dead.  ive checked battery,alt,cables,fuses,wiring and nothings wrong there.  now the amp light is on.  it starts sometimes for a week and then it wont start.then it may go a couple days and then it wont start again. if you use anything like air conditioner,radio,windows anything that draws battery it wont start. please help, im a female and dont know that much about cars.  thanks, lisa  

i just posted a question about my 93 olsmobile please help?  

do you have any tools... and a digital volt meter/???   they are under 20 bucks at most parts stores and places like harbor freight tools..

you need to test the voltage in the battery...    

engine off.. turn on the headlights for one minute.. to remove the surface charge...

set digital volt meter to 20 volts DC..

12.65 is a fully charged battery
12.45 is a 3/4 charged battery
12.25 is a half charged battery..

to go farther in this testing  you will need to have over 12.50 volts... to get an accurate reading.. if you voltage is below 12.5... you really need to have the battery charged on a battery charger at 10 amps for an hour.. or until the amp meter needle drops slightly from its maximum reading....

while the battery is out being charged...    i would go in with a stainless steel wire tooth brush and a jug of HOT water and clean the battery cable ends...   taking the bolts out of the rubber.. then verifying the ring terminal thats hidden inside the rubber boot is clean... you can use the hot water to warm the plastic. and a small screw driver to pry it over the ring terminal so you can get in there and clean the terminal with the wire brush and how water...


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dirty battery terminals will cause all kinds of problems... as will loose or corroded battery cables  and ground cables..


now.. if you have cleaned the battery cables...   and your battery is above 12.5 volts..

start the engine...  turn the headlights on...

1. measure the voltage from the positive battery post to the negative battery post...    14.1 to 14.8...

2. measure the voltage between the negative battery post and the engine block...    0.04 volts.. is acceptable..

3. measure the voltage between the negative battery post and the body...                  0.02 volts is acceptable.

4. measure the voltage between the engine block and the body...                              0.02 volts .. is acceptable..

this has taken me much longer to type this out than it will for you to do the test..


please post what you get....   i can tell more after you post them...

engine off...  drivers window down...     everything turned off...

disconnect one of the battery cables...       read how to connect your volt meter leads to the common connector on the front of your volt meter and the red lead to the 15 or 20 AMP DC hole in the front....

touch one lead to the disconnected battery cable...   the other to the battery post you disconnected it from....

so the meter is in line...    

if your car has NO shorts... you should get a reading of 0.030 MAX...   a normal reading for that car is 0.025 ...

do not turn on anything...   post results...

if you get more than the above reading...    you can start pulling fuses... till the reading drops back to this level...   note which fuse you are taking out... and take them out only ONE at a time...  

you will probably need to unplug the dome light fuse...    after you test with the doors closed....

the reason for the window open...   i have had cars self lock when i hooked the battery back up... locking me out of the car..  

a good rule of thumb for new cars is not to go more them 5 days with out starting the car up.