95 jeep wont keep runing

[gaen]

i have a 95 jeep grand cherokee that has been sitting on my driveway all summer, and now its time to get it runing for the winter. the computer was fried on it, so i bough a new/used one and instaled it, and i went to boost it with the batery reading 6.7volts(dead im assuming). boosted it with another car, kept the cables on for 20 min with the other car runing to hopefully charge the jeep, and everytime i take the cables off the jeep it will shut off. now the part that i dont undertand is when the jeep is shut off with no booster cables hooked up the battery reads 0.8 volts, and as soon as i unhook the positive and neg cables from the vehilce the battery read 10.6v. so is it that i have a dead battery, or would it be my alternator? becasue technically once the vehicle is running i should be able to unhook the cables with the vehicle running and it should stil be runing if the alt is good ? let me know what you think

Gaen,

Your battery is certainly discharged, and is likely in need of replacement. A very weak battery will often show voltage across its terminals when it is under no load (with nothing connected save for the voltometer). When given a load, however, a weak battery will often drop in potential to near 0 volts, as is the case with your battery. When you connect the battery to the car, even when the car is off, there is a load imposed upon it due to the dashboard clock, memory presets of the stereo, or cabin lights and such if the door is open.

Do you have a battery charger? A good test to ensure you do not replace a battery that is simply discharged is to leave it to charge for a while. An even better test involves the use of an ammeter. This measures electrical current in Amps. With nothing else connected to the battery, connect the jumper cables to the running vehicle and the dead battery. At the running vehicle, place the ammeter between the positive terminal and the positive line. This will show you the current flowing into the dead battery. A battery which is discharged, but still otherwise healthy, will draw between 10 and 15 Amps (for the average sized battery). A battery which needs replacement will draw very little, perhaps an Amp or two.

If you manage to charge the battery, and get the vehicle to start under its own power, put the voltmeter across the battery terminals with the vehicle running. If the charging system is working correctly, you should see around 13.5 to 14 volts. A dead alternator will show around 12 and falling.

A note of caution: if you do have a multimeter with an Ammeter built in, be careful how you use it. Make sure it can handle the 15 or so amps expected in the above test. Even more important: make sure you do not place the test wires across the battery (from + to -) when in ammeter mode. An ammeter is always connected IN LINE within a circuit, never across the source, as it is a very low resistance device, and placing it across a battery or similar voltage source constitutes a short circuit, which could result in damage to the system, or injury. (Likely it would result in a light show and the death of your multimeter, but still, be careful)

Jim

[blackfoot]

thats a good write jim!


lol graham did you forget everything you learned in school!!!


for starter change the battery! and if your still having problems try out a alternator.. but eitehr way by the sounds of it, your battery is toast!

[gaen]

thanks for your input jim! i picked up a batery charger today, and im going to try that.

[blackfoot]

if you got a bad cell from your battery falling off the deep end, then a charger wont help

Thanks Blackfoot :), and no problem Gaen, I hope it helps.

Yeah Gaen, as Blackfoot mentioned - if the battery is finished, it won't charge. But if it's a good deal, it's always a good idea to have a battery charger!

Jim

[gaen]

ya so i found one lyin in my old shop, good find, but doesnt work, lol. so im buying a new onetomorrow. thanks for your help guys!

[gaen]

so i bought the new battery charger, charged the battery, and when i took to cables off the batt the batt showed 12.6 and droping to finally 12.3. so i fig it was good. hooked it up to the jeep and started good, but shure enough batery read 11.8 and droping fast! so alternator def done, so now i ask who has an alternator for my 95 jeep cherokee, and what other vehicles would have the same alternator that i could use

Good work Gaen!

So you've found out it's not charging. Somewhere on your alternator exists the main line to the battery. With the car running, check at this point to see if power is coming out of the alternator. I had a cable corrode at this point, and although the battery wasn't charging, the alternator was working - the power just couldn't get there.

Be careful! The belt is dangerous, and it could pull in your voltometer or loose clothing. If you are nervous about this, one trick I've seen is to find a way to connect the voltometer to the alternator before you start the car, route the lines so nothing will get caught in the belts, and have the meter on before you start the car. Then just start it, look at the reading, and shut it down. No fussing around the belts while they are spinning.

Good luck,

Jim

short version: all that to say your alternator is likely dead, but testing to make sure is a good idea.

[blackfoot]

graham is pretty comfertable working around cars , hes a level 3 tech who got out of the trade lol.. seems like he forgot everything!

Heh oh ok. I wasn't trying to be condescending, I just wanted to make sure he was careful.

[gaen]

ya well i def had an awsome time taking that course!but i def forgot alotte!lol. and thanks jrfreeman, i will def try that test, very good idea. ill keep everyone posted on whats going on

[boostedd15b]

blackfoot Posted: Sat Oct 13, 2007 7:28 pm Post subject:

--------------------------------------------------------------------------------

thats a good write jim!


lol graham did you forget everything you learned in school!!!


for starter change the battery! and if your still having problems try out a alternator.. but eitehr way by the sounds of it, your battery is toast!



yeah . typical . whats a mechanic ... im a parts changer...
duh you should keep changing parts untill it works.

blackfoot Posted: Sat Oct 13, 2007 7:28 pm Post subject:

--------------------------------------------------------------------------------

thats a good write jim!


lol graham did you forget everything you learned in school!!!


for starter change the battery! and if your still having problems try out a alternator.. but eitehr way by the sounds of it, your battery is toast!




yeah . typical . whats a mechanic ... im a parts changer...
duh you should keep changing parts untill it works.

If you don't have something helpful to add, take it to smack with the other knuckle-draggers.

[Zenar]

I know it's a little late, but if your car stalls out as soon as you remove the jumper cables your alt is screwed, or like JF it's possible to have a connection from your alt to batt as well, some vehicals even have fuses on that line

[gaen]

i checked all the lines, and i replaced both battery terminals (no green ghost, lol) alternator is just not putting out enough power