[W126 Coupe] Re: battery drain

[Vance Rowley]

Basically, yes. Thanks for the tip. It's good to see and appreciated for any and all input, but this current draw that is draining the battery is intermittent. Putting a meter between the battery and terminal, the current most of the time is as specified and expected at between 85ma and 90ma which of course is fine. Its this intermittent peak up to 6amps that can stay on for from just a few seconds up to as much as 60 seconds. The time in between these peaks are not constant and could be anything from a matter of minutes to a matter of hours. 
Yep, you got it, this is a bastard of a fault to locate. In fact this problem has been going on now for around 5 years. But, as for most of those 5 years, I used the car on a daily basis. If you use the car every day, or even every other day, you wouldn't even know that there was a problem. Recently though, since I returned the car to the UK from Greece, I am not using the car as often. And yes, the battery itself is a 100amp/hour and absolutely perfect.

I have already recently ruled out the vacuum pump for the central locking system which all evidence pointed to and as a quick reminder, just about everything that is in the archives on this subject has been checked and is perfectly OK. If this current draw was a constant 6amps, then yes, your suggestion would most definitely be the way to go and should be quite easy to locate using your method and would under normal circumstances make perfect sense. Under these intermittent 6amp peak circumstances, you can imagine what it would be like trying to be lucky enough to have the peak present while taking a reading. I think I would stand more chance of winning the lottery. 

Dan Landiss is the star so far on suggestions on locating this problem by replacing all the fuses with say for example 1amp fuses. As the standard current draw from the battery is only 90ma, this intermittent 6amp peak should eventually blow one of the 1amp fuses with the car in standby (haven't tried this yet but thanks again Dan). This could be done overnight and completely unattended. This would at least give a better clue as to what circuits to check. Unfortunately, after looking at the circuit diagrams for these cars, each of the "hot at all times" fuses feed so many things, it could still be a nightmare to locate. But this is certainly the best idea I have heard so far to at least boil this problem down to what part of the electrics on the car is the cause.

Thanks anyway and keep the suggestions coming.

Regards,
Vance.


 
  ----- Original Message ----- 
  From: skorupa at aol.com 
  To: mbcoupes at mbcoupes.com 
  Sent: Wednesday, February 08, 2006 1:56 AM
  Subject: [W126 Coupe] Re: battery drain


  Have you checked the fuses with a meter. Most are  not live when the car is off and if one shows current then you caqn see where it's going. 


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