parasitic battery drain

J

Joblack

Member
Hello all,
I have a 2003 z4 which dies if it sits a day or two. The battery is less than a year old, I currently disconnect it when I park the car. I have tried pulling fuses with the battery connected and it still drops from sitting. Eventually I found that if I disconnect the alternator, the battery voltage goes from 12.6 to 12.3 over a 4 day span with the fuses in and the battery connected. The alternator charges the battery around 14.1 volts at idle. The alternator appears to pass a diode test. I pulled the brushes off the back of the alternator and all looks good.
Can anyone suggest any way to diagnose if I should replace the alternator assembly or the regulator/brush pack off the back to fix the battery drain?
Thank you
 
I am sure an expert will be along shortly. If it were me I would look for any aftermarket devices which might have been fitted as a starting point and try disconnecting these . Also check wether battery is the correct type and that terminals are all clean and tight. With my own car which is garaged I have it on trickle charge which works well and I also leave it unlocked.
Another thought might be to check that any courtesy lights are not stuck on/. I leave my boot ajar with the trickle charger so removed the boot light bulb to prevent any drain.
 
There are no after market parts on the car. The battery connections are clean. I disconnected the amp and stereo because the amp was water damaged long ago rendering the sound system useless. The climate control doesn’t work so no hot or cold air, I will disconnect it next. My passenger door has stopped unlocking a couple days ago as well as now the gas cap solenoid won’t release. The car is a family members who is overseas for a while. I have been trying to drive it a couple times a week to keep it fresh vs leaving it parked under a tree. I am a machinist by trade and a gear head by hobbie with 35 years of working on cars, bikes, and boats. This car is fun to drive and I would like to sort out its issues for my brother to enjoy when he returns home.
....now off to find a video on getting around my stuck fuel door
 
Hope you get it sorted. I am sure you know that when a battery, even a good one is discharged it is never the same again and possibly if it has gone flat a number of times then it will be pretty much useless. Also dont discount that the battery might not have been good to start with. If its a cheap make then that might simply be your problem.
 
I had some similar issues a while back and it was an iPod interface installed behind the radio. It was a BMW part I recall and there was an iPod connection lead in the glove compartment. Once that was disconnected all was good.
 
Mike, I agree with your words that a battery may not fully recover after a major discharge. I have confidence with this battery as I can leave the car for days and start it (if I disconnect the alternator while it sits).
I have also removed the boot light on the chance that I can’t see if it is stuck on and causing a drain.
I currently have the radio out and amp disconnected on the chance that they were causing any drain as the amp was damaged by water leaking into the boot years ago.
I was just pulling the gm5 module out, no signs of after market parts or any damaged wires.
Eventually after reinstalling the gm5 module the passenger door unlock worked from the central switch as well as unlocking with the key.
I am happy that I can open the passenger door again, just hesitant to lock it as I live in a very safe area and nothing is ever left in the car. I am happy to now know how to open the gas filler door when that fails to unlock.
Thank you for your thoughts Mike and James, the hunt continues regarding the battery drain and climate control failure
 
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