[W126 Coupe] Long term Battery drain problem

[Vance Rowley]

Hi Bellamy,

 I am not going to jump to conclusions just yet. Although I have definitely confirmed it is one of the circuits on fuse #2, I only had the relay removed and fuse #2 replaced for 2 days. But the battery voltage was so good and the car started so well, it most certainly looks like the combination relay. However it normally takes 3 days to drain the battery enough for a failed start. Anyway, just to try and speed things up, I have again replaced the relay but this time removed fuse #3 which feeds the rear heated window (through the combination relay). One more problem has just cropped up while doing this though. That is when I removed the relay, the alarm system which also has keyless entry stopped working. This was expected while this relay was out, as it feeds the hazards which will normally flash 3 times when armed and once when not. So my Meta alarm system is tied in somewhere with this relay. But I replaced the relay a couple of hours ago and as I said took out fuse #3. But the alarm still won't arm, or activate the central locking system with the key fob. It won't even de-activate the immobilizer (which just normally one quick press of the key fob does the job) luckily I have a manual electronic key to de-activate the immobilizer that I insert into the centre console, so I can start the car. It looks like I might need to re-boot the alarm system by disconnecting the battery for a while. I will try that tomorrow.

Cheers,
Vance
  ----- Original Message ----- 
  From: Mister McGoo 
  To: mbcoupes at mbcoupes.com 
  Sent: Tuesday, March 14, 2006 5:40 PM
  Subject: Re: [W126 Coupe] Long term Battery drain problem


  Vance;

  You have narrowed it down to functions on circuit 30 that go through the Combination Relay.  You need to identify which function.  But the combintion relay appears (so far) to be central to the problem. 

  You likely have to find the offending component through a process of elimination.  You could eliminate the relay itself by switching it with a known good one, or if you can not borrow one, replacing it with a new one ( it costs about $75).  

  I'd do that first to confirm that the relay is good.

  If that fails to solve the problem then you can tackle the individual functions (circuits) one at a time.

  -Bellamy




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    From:  "Vance Rowley" <vance.rowley at tiscali.co.uk>
    Reply-To:  Vance Rowley <vance.rowley at tiscali.co.uk>,Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
    To:  "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
    Subject:  Re: [W126 Coupe] Long term Battery drain problem
    Date:  Tue, 14 Mar 2006 16:45:48 -0000
    >Hi Jim,
    >
    >   Good point. I don't think your idea is "off the wall" at all. I think it could well be a very good possibility. I will put it on my list of things to check out.
    >
    >Cheers,
    >Vance.
    >
    >----- Original Message -----
    >From: "Jim Ham" <jimham at porcine.com>
    >To: "Vance Rowley" <vance.rowley at tiscali.co.uk>; "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
    >Sent: Tuesday, March 14, 2006 4:35 PM
    >Subject: Re: [W126 Coupe] Long term Battery drain problem
    >
    >
    > > I'd take a close look at the wipers. 6A is about right for a stalled wiper
    > > motor. The parking switch is a wiping contact, so with age or misadjustment
    > > the contact may be on the hairy edge of making or not making when the
    > > wipers are mechanically parked. Under these conditions temperature and
    > > humidity could cause the contact to intermittently make.
    > >
    > > This may seem off the wall, but it seems that most solutions at this point
    > > are pretty implausible.
    > >
    > > Regards,
    > >
    > > Jim Ham
    > >
    > >
    > > At 07:36 AM 3/14/2006, you wrote:
    > >>Hi Steve,
    > >>
    > >>  I was thinking about that, but I think I might try the rear heated
    > >> window first just to prove the theory on that one either is,or isn't correct.
    > >>Thinking about it, you are most likely correct about the contacts being
    > >>corroded or poor to say the least. One thing I didn't mention previously
    > >>is the last time I drove the car and needed the rear heated window to
    > >>de-mist, it didn't seem to be working very well. It used to. So putting 2
    > >>and 2 together, bad contacts would certainly be suspect on that one.
    > >>Trouble is though, with this relay having a timer built into it, it ties
    > >>in with the intermittent current draw and could be more likely the timer
    > >>circuit coming on and off randomly and still feeding the heated window.
    > >>Only difference being it's not getting the full current because of bad or
    > >>dirty contacts.
    > >>
    > >>All speculation at this point, but once I have tried replacing the relay
    > >>and pulled fuse#3 and got a result (one way or the other) I will take it
    > >>from there and then open up the relay.
    > >>
    > >>Thanks,
    > >>Vance
    > >>
    > >>
    > >
    > > <snip>
    > >
    > >
    > > Porcine Associates
    > > +1.650.326.2669
    > > www.porcine.com
    > >
    > >
    >The MB Coupes Website!
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    >Postings remain property of MB Coupes, L.L.C.



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