'99 A6 battery drains in 2-3 days if car not used
11-27-2010, 07:42 AM
#1
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'99 A6 battery drains in 2-3 days if car not used
'99 A6 AVANT 145K. Battery drains down in 2-3 days if car not used. Battery is new. Thought old battery ( 5 years old) wasn't holding charge.
Will a computer hook up show where the problem may be ? (error codes)
Is there a way of isolating circuits ? Can you measure amps/volts @ battery while pulling fuses to isolate which circuit is causing the problem ?
Are there some typical culprits in this vintage A6 that could be checked ?
Thanks.
Will a computer hook up show where the problem may be ? (error codes)
Is there a way of isolating circuits ? Can you measure amps/volts @ battery while pulling fuses to isolate which circuit is causing the problem ?
Are there some typical culprits in this vintage A6 that could be checked ?
Thanks.
11-27-2010, 09:44 AM
#2
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Classic drain is inside light in back is on when hatch is closed. Get inside, close the hatch, and see. You can get out either with your keyfob or someone lets you out. Make sure a friend is around...LOL.
You isolate circuits buy pulling fuses. It helps to have a handful of fuses in case of shorts. It is possible to wire up an ammeter to a blown fuse for a test device, but the fuses are pretty small.
BTW...a new battery can fail too. Before you go through all this, charge the battery for 24 hours with the negative ground cable disconnected. Let the battery sit for three days and then load test it. If it is still good, then you are sure you have a battery problem.
OTOH, if you can't wait several days w/o using the car, you can always use an inductive ammeter (I like Fluke's clamp-type) over the positive cable and see how much drain you have with the car supposedly all shut down. The battery is something like 70amp-hours (?) so if you have a one-amp drain it will kill the battery in 70 hours or usually much less. I've left my S6 parked for a couple weeks with no battery drain/kill so I would guess the sitting battery drain should be less than 200milliamps.
If you have more than this, start pulling fuses to see which circuit is sucking.
You isolate circuits buy pulling fuses. It helps to have a handful of fuses in case of shorts. It is possible to wire up an ammeter to a blown fuse for a test device, but the fuses are pretty small.
BTW...a new battery can fail too. Before you go through all this, charge the battery for 24 hours with the negative ground cable disconnected. Let the battery sit for three days and then load test it. If it is still good, then you are sure you have a battery problem.
OTOH, if you can't wait several days w/o using the car, you can always use an inductive ammeter (I like Fluke's clamp-type) over the positive cable and see how much drain you have with the car supposedly all shut down. The battery is something like 70amp-hours (?) so if you have a one-amp drain it will kill the battery in 70 hours or usually much less. I've left my S6 parked for a couple weeks with no battery drain/kill so I would guess the sitting battery drain should be less than 200milliamps.
If you have more than this, start pulling fuses to see which circuit is sucking.
11-27-2010, 09:46 AM
#3
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Another drain could be a light under the hood/bonnet if you have one.
Old days these lights were controlled with mercury-loaded switches but I think those switches are no longer used due to mercury vapor issues. If the gravity or position-sensing switch fails on, the light will be on with the hood closed.
Old days these lights were controlled with mercury-loaded switches but I think those switches are no longer used due to mercury vapor issues. If the gravity or position-sensing switch fails on, the light will be on with the hood closed.
11-27-2010, 05:49 PM
#4
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enough guessing .. lets get down to troubleshooting .. get your multi meter and set it to amps ( current) . Disconnect the positive battery cable and atatch one meter lead to it .. atach the other meter lead to the battery .. you are now measuring current drain on the car .. not sure what nominal is on these cars but i would expect much more than about 20 - 30 ma ( make sure you have radio code before starting ) .
Then start popping fuses,, after each one check your battery drain and see which one makes the biggest difference . You are now troubleshooting.
if you pop all the fuses and still have a big drain it could be a shorted diode in your bridge rectifier of your alternator. you will have to disconnect your alternaot to isolate that but one thing at a time ..
Good luck
Then start popping fuses,, after each one check your battery drain and see which one makes the biggest difference . You are now troubleshooting.
if you pop all the fuses and still have a big drain it could be a shorted diode in your bridge rectifier of your alternator. you will have to disconnect your alternaot to isolate that but one thing at a time ..
Good luck
11-28-2010, 01:35 PM
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Thanks to all for assistance. Before starting a major test I just pulled the 5amp and 20amp fuse for "door control." I think that did it. Car started easily after sitting one day. Will give it one more day to see if battery stays strong. If so, it seems either one or both circuits seem to be the source of the problem. Have not gone through the wiring diagrams but would assume the 20amp fuse is in the circuit with the control box.
tullheinz
tullheinz
11-29-2010, 01:17 PM
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If you keep killing your battery and recharging it you'll end up replacing the battery....I'ma just sayin...
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03-26-2011, 11:42 AM
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A6 battery drain.
enough guessing .. lets get down to troubleshooting .. get your multi meter and set it to amps ( current) . Disconnect the positive battery cable and atatch one meter lead to it .. atach the other meter lead to the battery .. you are now measuring current drain on the car .. not sure what nominal is on these cars but i would expect much more than about 20 - 30 ma ( make sure you have radio code before starting ) .
Then start popping fuses,, after each one check your battery drain and see which one makes the biggest difference . You are now troubleshooting.
if you pop all the fuses and still have a big drain it could be a shorted diode in your bridge rectifier of your alternator. you will have to disconnect your alternaot to isolate that but one thing at a time ..
Good luck
Then start popping fuses,, after each one check your battery drain and see which one makes the biggest difference . You are now troubleshooting.
if you pop all the fuses and still have a big drain it could be a shorted diode in your bridge rectifier of your alternator. you will have to disconnect your alternaot to isolate that but one thing at a time ..
Good luck
Drain with all fuses in was 300ma to 400ma with VOM meter. Needle at the 10a setting scale sat at .3 and at the 300ma setting hit top of scale.
Therefore my estimate as between 350 and 400 ma.
I pulled each circuit fuse and watched meter. I measured at both the 10a and the 300ma setting. There was no discernible change on any circuit. The only thing I noticed is that each time I completed the circuit by plugging test lines into the meter, the load would jump to about 2 amps and then drop down ( in about 10 seconds) to the normal load 400 ma+/-. During this event I would hear a slight humming noised from the alternator area.
Currently, as car is garaged, I simply disconnect the battery neg terminal. Battery hold charge for weeks, and alternator charges battery with normal use.
Could alternator still be the problem ?
Thanks
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