battery wont keep charge?
12-15-2007, 02:56 PM
#21
Join Date: Dec 2007
Location:
Posts: 32
RE: battery wont keep charge?
i have heard that its not a good way to chek for cars made after 93, but for his year car this is one way to check the alt. and after running this test on my stang i had no problems with the car, but i am pretty sure this isnt the safest way to check but it duz make it a little easier
12-18-2007, 03:09 PM
#22
RE: battery wont keep charge?
ORIGINAL: mjr46
[sm=wtf.gif][sm=wtf.gif][sm=WTFsgign.gif][sm=yikesomg.gif][sm=noooo.gif]...uhhh no!!!!!! any car will die when you do that because you are removing the ground by which all systems are operating off of......and that's a good way to cause a voltage spike and take out a ecm
....never remove the cables while the car is running and when the car shuts off that does not indicate a bad alt!! that is not even a valid test you are speaking of and has no relation to the charging output test and or ability of the alt to charge.....to correctly test an alt you need a multimeter with a voltmeter function and or amps function to test voltage and amperage output......and the way you test for that is place the system under a load by turning on all accesories which will place a load on the alt and field the alt so it starts outputing more amperage to supply the proper amount of current to the demands required....or just simply use a VAT 40/45 to run the test
[sm=wtf.gif][sm=wtf.gif][sm=WTFsgign.gif][sm=yikesomg.gif][sm=noooo.gif]...uhhh no!!!!!! any car will die when you do that because you are removing the ground by which all systems are operating off of......and that's a good way to cause a voltage spike and take out a ecm
....never remove the cables while the car is running and when the car shuts off that does not indicate a bad alt!! that is not even a valid test you are speaking of and has no relation to the charging output test and or ability of the alt to charge.....to correctly test an alt you need a multimeter with a voltmeter function and or amps function to test voltage and amperage output......and the way you test for that is place the system under a load by turning on all accesories which will place a load on the alt and field the alt so it starts outputing more amperage to supply the proper amount of current to the demands required....or just simply use a VAT 40/45 to run the test
12-18-2007, 03:31 PM
#23
6th Gear Member
Join Date: Nov 2005
Location: Rochester, NY
Posts: 8,467
RE: battery wont keep charge?
If when the car is running all the electrical stuff runs slow and the lights are dim my bet is on the alternator. I've experienced this 3 times so far, your alt can still make enough voltage to run and drive but if you let it idle for too long the voltage can drop and end up draining your battery. Easiest way to check is to put a voltage meter on your battery when your car is idling, if it's 13-14 volts you're fine. If you turn the car off and the voltage at the battery stays above 12 the battery is probably fine. Lastly don't always rely on the autpart store testing your parts, they have given me bad info about both alts and batteries. Sometimes you just gotta use common sense.
12-18-2007, 05:30 PM
#24
RE: battery wont keep charge?
ORIGINAL: OnyxCobra
If when the car is running all the electrical stuff runs slow and the lights are dim my bet is on the alternator. I've experienced this 3 times so far, your alt can still make enough voltage to run and drive but if you let it idle for too long the voltage can drop and end up draining your battery. Easiest way to check is to put a voltage meter on your battery when your car is idling, if it's 13-14 volts you're fine. If you turn the car off and the voltage at the battery stays above 12 the battery is probably fine. Lastly don't always rely on the autpart store testing your parts, they have given me bad info about both alts and batteries. Sometimes you just gotta use common sense.
If when the car is running all the electrical stuff runs slow and the lights are dim my bet is on the alternator. I've experienced this 3 times so far, your alt can still make enough voltage to run and drive but if you let it idle for too long the voltage can drop and end up draining your battery. Easiest way to check is to put a voltage meter on your battery when your car is idling, if it's 13-14 volts you're fine. If you turn the car off and the voltage at the battery stays above 12 the battery is probably fine. Lastly don't always rely on the autpart store testing your parts, they have given me bad info about both alts and batteries. Sometimes you just gotta use common sense.
12-18-2007, 07:59 PM
#25
D.R. THE PATHETIC DORK
Join Date: Jun 2007
Location: West Virginia
Posts: 30,863
RE: battery wont keep charge?
ORIGINAL: shawnk007
Very wrong MJR46! Current would flow from the alternator back to the alternator case. Go out to your car, run the engine and disconnect your battery. Assuming that you have a good alternator, you wouldn't be able to then tell me that your car died. Taking the battery out of a running vehicle would just cause more stress on the alternator, and as previously stated, could cause damage on a modernized computer controlled vehicle. Also, you have the earth's natural ground that your standing on. Why do you think telephone poles dont have ground wires?
ORIGINAL: mjr46
[sm=wtf.gif][sm=wtf.gif][sm=WTFsgign.gif][sm=yikesomg.gif][sm=noooo.gif]...uhhh no!!!!!! any car will die when you do that because you are removing the ground by which all systems are operating off of......and that's a good way to cause a voltage spike and take out a ecm....never remove the cables while the car is running and when the car shuts off that does not indicate a bad alt!! that is not even a valid test you are speaking of and has no relation to the charging output test and or ability of the alt to charge.....to correctly test an alt you need a multimeter with a voltmeter function and or amps function to test voltage and amperage output......and the way you test for that is place the system under a load by turning on all accesories which will place a load on the alt and field the alt so it starts outputing more amperage to supply the proper amount of current to the demands required....or just simply use a VAT 40/45 to run the test
[sm=wtf.gif][sm=wtf.gif][sm=WTFsgign.gif][sm=yikesomg.gif][sm=noooo.gif]...uhhh no!!!!!! any car will die when you do that because you are removing the ground by which all systems are operating off of......and that's a good way to cause a voltage spike and take out a ecm
....never remove the cables while the car is running and when the car shuts off that does not indicate a bad alt!! that is not even a valid test you are speaking of and has no relation to the charging output test and or ability of the alt to charge.....to correctly test an alt you need a multimeter with a voltmeter function and or amps function to test voltage and amperage output......and the way you test for that is place the system under a load by turning on all accesories which will place a load on the alt and field the alt so it starts outputing more amperage to supply the proper amount of current to the demands required....or just simply use a VAT 40/45 to run the test
12-18-2007, 09:30 PM
#26
RE: battery wont keep charge?
ORIGINAL: mjr46
Ahh yes but you don't drive telephone poles...or do you???....anyway well the principal stated above may hold true for older vehicles as long as you understand it doesn't always work for newer vehicles where the alt field circuit is controlled via the ecm and or where a vehicle is CAN compatible..it's not gonna work on the newer cars....and if you don't beleve me go try it on a new BMW or a New Mercedes.......hAD a theft recovery not to long ago come in on a new bmw and one of the techs was trying to do that and remove the jump pack after starting it...almost f'ed up stuff had we not caught him in time.
Ahh yes but you don't drive telephone poles...or do you???....anyway well the principal stated above may hold true for older vehicles as long as you understand it doesn't always work for newer vehicles where the alt field circuit is controlled via the ecm and or where a vehicle is CAN compatible..it's not gonna work on the newer cars....and if you don't beleve me go try it on a new BMW or a New Mercedes.......hAD a theft recovery not to long ago come in on a new bmw and one of the techs was trying to do that and remove the jump pack after starting it...almost f'ed up stuff had we not caught him in time.
12-18-2007, 10:09 PM
#27
D.R. THE PATHETIC DORK
Join Date: Jun 2007
Location: West Virginia
Posts: 30,863
RE: battery wont keep charge?
ORIGINAL: shawnk007
I may........
ORIGINAL: mjr46
Ahh yes but you don't drive telephone poles...or do you???....anyway well the principal stated above may hold true for older vehicles as long as you understand it doesn't always work for newer vehicles where the alt field circuit is controlled via the ecm and or where a vehicle is CAN compatible..it's not gonna work on the newer cars....and if you don't beleve me go try it on a new BMW or a New Mercedes.......hAD a theft recovery not to long ago come in on a new bmw and one of the techs was trying to do that and remove the jump pack after starting it...almost f'ed up stuff had we not caught him in time.
Ahh yes but you don't drive telephone poles...or do you???....anyway well the principal stated above may hold true for older vehicles as long as you understand it doesn't always work for newer vehicles where the alt field circuit is controlled via the ecm and or where a vehicle is CAN compatible..it's not gonna work on the newer cars....and if you don't beleve me go try it on a new BMW or a New Mercedes.......hAD a theft recovery not to long ago come in on a new bmw and one of the techs was trying to do that and remove the jump pack after starting it...almost f'ed up stuff had we not caught him in time.
I'd love to see a pic
12-18-2007, 10:17 PM
#28
6th Gear Member
Join Date: Nov 2005
Location: Rochester, NY
Posts: 8,467
RE: battery wont keep charge?
ORIGINAL: shawnk007
Even if your putting out 13-14 volts, you still might not be putting out enough amperage....
ORIGINAL: OnyxCobra
If when the car is running all the electrical stuff runs slow and the lights are dim my bet is on the alternator. I've experienced this 3 times so far, your alt can still make enough voltage to run and drive but if you let it idle for too long the voltage can drop and end up draining your battery. Easiest way to check is to put a voltage meter on your battery when your car is idling, if it's 13-14 volts you're fine. If you turn the car off and the voltage at the battery stays above 12 the battery is probably fine. Lastly don't always rely on the autpart store testing your parts, they have given me bad info about both alts and batteries. Sometimes you just gotta use common sense.
If when the car is running all the electrical stuff runs slow and the lights are dim my bet is on the alternator. I've experienced this 3 times so far, your alt can still make enough voltage to run and drive but if you let it idle for too long the voltage can drop and end up draining your battery. Easiest way to check is to put a voltage meter on your battery when your car is idling, if it's 13-14 volts you're fine. If you turn the car off and the voltage at the battery stays above 12 the battery is probably fine. Lastly don't always rely on the autpart store testing your parts, they have given me bad info about both alts and batteries. Sometimes you just gotta use common sense.
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