[W126 Coupe] Update on Battery Drain

[Iain Gunn]

Can you run some heavy connection wires from the battery to somewhere 
underneath the car, say at the tow hook door and run a small trickle charger 
on it when you are not driving? There is a system that I sold years ago 
called Safe T Connect, http://www.superiorsignals.com/safetconnect/stc1.html 
Sold this mostly to tow truck drivers, you could run these to the front of 
the vehicle, and mount on the grill or at the back of the vehicle mounted to 
the bumper. They had silver coated connections and they were set for no 
fault connections for jumper cables. You just connected to jumpers to the 
battery and plugged into the plug. Red and green polarity lights lit up to 
make sure that you had proper orientation on the vehicle to be jump started.
----- Original Message ----- 
From: "Vance Rowley" <vance.rowley at tiscali.co.uk>
To: <mbcoupes at mbcoupes.com>
Sent: Monday, February 20, 2006 8:17 PM
Subject: [W126 Coupe] Update on Battery Drain


> Hi Guys,
>
>
>  I am almost at a loss on this one. I contacted my local Meta dealer and 
> spoke at length with him regarding the possibility of my alarm/immobilizer 
> being the problem. Basically the answer is 99.9% chance it isn't. I also 
> looked on some forums and found the backup battery is built into the alarm 
> sounding unit. I have already run a test with this disconnected, but this 
> intermittent current draw was still there, so there goes the theory of the 
> backup battery taking the current.
>
> I have tried replacing all the fuses that are "hot at all times" with 1amp 
> fuses. Left them in overnight, but all were still OK next day, but the 
> current draw had obviously happened overnight as the engine only just 
> turned over. I even went to my local car accessory place and did another 
> drop test on the battery, hoping that although my last tests showed the 
> battery was OK, that maybe I was mistaken somehow. It tested perfectly and 
> yes it's charging perfectly too.
>
> It looks like something that must be connected on "the other side of the 
> fuses" that must be taking this intermittent current draw, comming 
> directly from the battery. The factory alarm is disconnected completely. 
> This was done when the Meta system was fitted and this problem, although 
> has being going on for years, it hasn't always been there. I have had the 
> car parked up (shortly after I bought it) for two weeks with the alarm 
> armed and when I returned and started it, it was as if it started on a 
> brand new battery.
>
> I have even completely had the after market stereo system disconnected in 
> case for some reason this might take an intermittent current draw. No luck 
> there either. The normal current draw at the battery terminal is at 
> between 85ma and 90ma with the alarm / immobilizer armed and everything 
> connected. But something is taking this intermittent 6amps or so now and 
> then. I even stood watching the meter (connected between the battery and 
> terminal) for nearly an hour today, but didn't even see this once within 
> this time period. In the past I have seen it, but it's so intermittent, 
> you have got to be very lucky to be in the position to measure and see it. 
> Even then, because it's not there all the time, what chance is there of 
> finding out what it is?
>
> As you know from previous posts, I have ruled out the vacuum pump that 
> feeds the central locking system and all of the normal checks have been 
> made, but there is nothing in the archives (at least not until now) on an 
> intermittent problem like this one. I am basically out of ideas. Am I the 
> only one with a 560SEC that this has happened to? I welcome any ideas and 
> I am at a stage where I would not consider any idea a stupid one. The only 
> idea I have myself is to just drive it every day, which is what I used to 
> do, so that idea is ruled out at the moment. And yes, the other idea is to 
> disconnect the battery when not in use. This I was doing, but by ideas and 
> suggestions, I mean to find the problem, not just cure the symptoms.
>
> Completely mystified.
> Vance
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>
>
>
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