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new battery dead?

 
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mattalme mattalme
New User | Posts: 3 | Joined: 10/09
Posted: 10/10/09
10:23 PM

so my dad bought me a used 98 jeep grand cherokee laredo and had it serviced bumper to bumper. this car has 160k miles. kept it in phoenix for about a week drove it every day everything was fine with it. then drove it all the way up to north dakota, not a problem. now i've had it for about a week, no problems what so ever and just today i went to start it and the battery was completely dead. lights weren't left on, nothing. like i said battery is new and has been in there a few weeks. could this be a sign of a bad alternator? wouldn't they catch that if it was serviced bumper to bumper? suggestions or ideas?  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/10/09
11:05 PM

see if the slide switch under the head light switch is pushed all the way to the right.. if so.. that will turn on the interior lights.. and drain the battery... and most people won't notice it.. unless it's night.. or you actually look..

have the battery recharged...  10 amps for 2 hours should do it..  anything more than 10 amps and you can overheat the battery...

but the alternator can put out 100 amps or more.. yes.. but the alternator runs most of the items in the car..  and the battery is never that low..

charging a totally discharged battery will usually ruin or shorten the life of the alternator...    alternators are just not designed to charge a deeply discharged battery...  they are designed to keep the car and the accessories operating and to top off the battery after it starts the car...   usually less than 1 percent discharge ...

if you need to jump a car with a really deeply discharged battery...     hook up jumper cables... let the car thats running.. charge the battery is the dead car for like 10 minutes...     then turn off the car thats running and start the car that had a dead battery... this will part way charge the battery...  and turning the others cars engine off.. protects that cars alternator from the huge amount of surge when the other car is cranked..  

mattalme mattalme
New User | Posts: 3 | Joined: 10/09
Posted: 10/12/09
07:25 PM

so my car has been sitting for as long as it did when i found it with the dead battery. the battery is at normal levels, and everythings fine. i know for a fact no lights were left on or anything the day i found it dead but i'm really confused now to why that would have happened. could there be a short somewhere or something? what could be going on?  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/12/09
11:25 PM

with the battery fully charged...    open the hood.. roll down the drivers window...     with the engine off.. disconnect one battery cable...   put a 12 volt test light between the battery post and the disconnected cable..  if it lights up.. you have draw..

you can pull fuses one at a time and put them back before pulling the next one...  and see if the test light goes out..

a digital volt meter with a 10 amp DC or 15 amp DC setting is what mechanics use..    hooked between a disconnected battery cable and the post were it went..     the wires go into different places with this test.. and be careful not do go from positive to negative with the test leads plugged into the amp meter ports..  you will blow up the volt meter..

are you sure the battery is good... sometimes when they get a few years old.. they won't hold a charge..  

mattalme mattalme
New User | Posts: 3 | Joined: 10/09
Posted: 10/16/09
04:40 PM

took it to a repair shop and had the guys there check it for a draw(which cost me a splendid $70 is that normal?) and they said i had a draw of 400 milliamps from the switch in the very back in the tail gate that tells if it's open or not. the picture of the car right under the ac controls that tells you what doors are open or not doesn't work so they said if that worked i would have been able to tell that the switch back there was shorting out because the switch was saying it was open when they checked it which it wasn't. i asked them if i could just unplug said switch that tells if the tail gate is open or not because the thing under my ac that tells which doors are open doesn't even work so it seemed to me that having that switch was pointless. the guys there said it could be VERY HARMFULL to my cars computer and they highly suggested that i didn't do that. do you think this would really harm my cars computer if it wasn't receiving a signal from only one switch? thoughts and comments on this experienced would be much appreciated.  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/16/09
08:07 PM

i will have to check into that...   some cars have many computer controlled circuits..  

some of the newer jeeps have tons of them..

you might look at the autozone.com web site..  they have wiring diagrams online..  if i get a chance.. i will do some studying ..  

Atechstudent Atechstudent
New User | Posts: 14 | Joined: 10/09
Posted: 11/05/09
02:26 PM

lol, disconnecting that switch will in no way harm your cars electronics. If it is causing a parasitic voltage draw, ie. 400milliamps then disconnect it. 70 dollars for a correct diagnosis at a shop is very good. I have heard stories of people spending hundereds to over a thousand dollars on repairs that didnt fix the problem and still did not get an accurate diagnostic.  

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