Detailed step by step diagnostic DIY ... dead battery ... parasitic current drain
PLEASE IMPROVE THE STEPS BELOW SO ALL BENEFIT!
(Advice is always welcome!)
EDIT: Updated as per Fudman to pull the FSU rather than fuse F76.
EDIT: Updated as per 540iman that the nature of the current draw implicates certain circuits.
EDIT: Updated as per edjack in that the four doors must be shut in order for the computers to go to sleep.The last few days, twice now, I go out to the bimmer, and, ... well ... nothing.
No click. No lights. No horn. No nuthin'.
At first, I thought I had left the lights on or maybe I had charged too much portable electronics - but I wouldn't have done that twice.
So as to add value with every repair, here's my story, as it unfolds (so that others can follow suit in the future).
a) I had put in a new (acm Germany) FSU in, oh, about three years ago (need to check) <=== here's the thread ... 2/2/2009
b) I had put in a rebuilt (Bosch 120A) alternator & belt drive system a couple of years ago (need to check) <=== here's the thread 7/26/2010
c) I had put in a new (Duralast 49DL) battery just over a year ago (need to check) <=== here's the thread ... 9/19/2011
Active period: The first 16 minutes after you exit the vehicle, shut all doors, and then open the trunk (as evidenced by the indicator light by the shift lever being lit).
Quiescent period: After 16 minutes, the computers shut down, and that orange indicator light by the shift lever goes off.
Note: Most say you should see something like 30 ma quiescent draw AFTER the car shuts down at 16 minutes (but I'm seeing 80 milliamps on my 2002 525i).
Flowchart: (thanks to Fudman & 540iman for updating the overall procedure)
Step 1: Disconnect & charge the battery (I use a 4 amp charger - I wish I had a 6 amp charger though)
Step 2: Drive to Autozone (or equivalent) to have the charging system tested (or test it yourself with a DMM, using this procedure).
Step 3: If it passes step 2, then measure parasitic drain (active & quiescent) with and without the FSU in series with the negative battery terminal
Step 4a: If you find double-digit current draw, then pull the FSU, and check current draw again (both active & quiescent)
Step 4b: If you find single-digit current draw, then pull fuse F56, and check current draw again (both active & quiescent)
Step 4c: If if it's neither of those culprits, then start pulling all 88 fuses, one by one, with an ammeter in series with the battery
Note: You 'can' pull the 40A yellow blower circuit fuse F76 for step 4a - but for reasons Fudman explains, it's better to pull the FSU instead.
0. Print the fuse lists from EF1 to EF5, and from F1 to F114 for each of the six fuse panels (see detailed fuse listing below)
1. For obvious reasons, keep your ignition key somewhere safe OUTSIDE the vehicle (e.g., in the trunk lock or in your pocket)
2. Open the trunk and leave it open; shut all four doors; & lock the vehicle using the key fob (taking note of the orange light near the shift lever)
3a. With a 10mm socket on a 6-inch extension, remove the battery negative cable
3b. Optional: Discharge stored charge in the electronics by temporarily disconnecting BOTH battery cables, and shorting the two CABLES with a wrench (do not short the battery terminals!)
3c. Reconnect the battery positive cable if you performed optional step 3b above.
4a. Set your ammeter to the 20 amp or 10 amp range (whichever you have that is highest)
4b. Hook the positive (red) lead to the brown negative battery cable (use a clamp or alligator clips to attach)
4c. Hook the negative (black) lead of the ammeter to the bare negative battery post (I used a heavy gauge wire with large alligator clips on each end to attach)
5. Work the meter range down from amps to milliamps (you must be ready for up to 20 amps - but you want to see something around 2 amps active to less than 100 ma quiescent)
6. With the ammeter still connected, wait for shut down (about 16 minutes) as indicated by the automatic transmission console light going off
Note: Some DMMs shut off automatically about 10 or 15 minutes into your test, so you'll need to activate those DMMs periodically.
7. Make a note of the TOTAL current drain after shutdown (all lights should be off)
8a. If current drain is around 2 amps active and less than 100 ma quiescent, then you're probably OK
8b. If current drain fluctuates in the teens at any time (active or quiescent), then pull the FSU & retest
8c. If current drain is in the single amps (quiescent period), then pull fuse F56 & retest
9. If neither the FSU nor fuse F56 make a difference and your current draw is still greater than about 100ma quiescent, then it's time to debug by pulling the fuses, one by one
10. Disconnect your ammeter, re-connect the battery, again wait for shutdown - and then, one by one, pull the 88 fuses, putting your ammeter leads across the open contacts
Note: Unfortunately, some fuses, when pulled, will wake the car up and force you to wait anywhere from 1 minute to the full 16 minutes to continue
11. You can either remove and immediately replace each fuse, or, you can successively remove all fuses sequentially (starting with the lowest amperages first)
12. Write down the parasitic drain for each fuse & troubleshoot the circuit with the highest parasitic drain.
Unfortunately, my Fluke 75 requires me to move the leads to go from the 10Amp range down to the 300ma range (which resets the car!).
Note: You can measure total parasitic drain in series with the battery, or individually, across each fuse's terminals.
For the record, this is what the battery charger did last night & this morning:
Last edited by bluebee; 02-09-2013 at 11:25 AM.