[s-cars] Battery update, C4 A6

[Huw Powell]

> I need to go through the debugging routine. If anyone wants to correct me 
> on this, please do.
> 
> Finding a battery drain:
> 
> 1. Disconnect the + cable at the battery.
> 
> 2. Connect a DVM between the + terminal and the + cable. 
> 
> 3. Set the DVM to measure milliamps (and don't try starting the car).
> 
> 4. Note the amperage you are starting with. (If it is less than X ??? ma, there is no drain. The radio (memory) and alarm system? will produce a minor drain on the battery. We are looking for a bigger drain that kills the battery in a week or two.
> 
> 5. Pull one fuse at a time. Note the change in amperage.
> 
> 6. When you pull the fuse that makes the amperage approach 0, you've found the drain.
> 
> 7. Replace that fuse and keep going; you may have a 2nd drain on the battery.
> 
> 8. Determine which loads are protected by the fuse identified in step 6 (or 7). 
> 
> 9. One at a time, remove each load to see which one is causing the drain.
> 
> 10. Repair or replace the problem found in step 9.
> 
> Comments and corrections welcomed, especially the minimum value that is an acceptible drain.

I would add to #3 (and put it "first") "Don't even put the key in the 
ignition.  Do this with all the doors shut and timered interior lights 
off.  Don't open any doors or the trunk with the meter in the circuit."

As far as an acceptable drain, 50 mA or so ought to run the clocks and 
memory in the radio.  Some have suggested a bit higher is acceptable.

We could determine this if someone with a "healthy" car makes the 
mesurement, or even on an "unhealthy" car, the tester could remove the 
fuse that powers the clock and radio and see how much the current drops 
(of course, if the gremlin is on this circuit, this won't tell us anything).

Oh, and the alternative to the DVM in #2 (etc.) is to use a light bulb, 
and watch for its brightness to drop when loads are removed.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/