[W126 Coupe] Long term Battery drain problem

[Vance Rowley]

Well Guys, looks like we are aiming in the right direction. As on my previous post, you will know I have replaced fuse #2 which it was confirmed with this removed the battery drain stopped, but removed Relay "B" from the fuse box, which is just one of the many circuits fed by fuse #2. According to the info I have, this relay is a combination relay which controls 1. Turn Signals, 2.Hazard lamps and 3.Wiper /Washer. Bottom line is without this relay plugged in, the battery does not drain. Trouble is everything seemed to be working as it should when the relay was fitted. So now it comes down to either the relay unit itself is causing this intermittent current draw, or one of the circuits that it feeds. 

I started up the car today without the relay to check exactly what was and wasn't working without it. I found that even though the manual says that this relay controls the wiper/washer, the wipers themselves actually worked but would not self park. The washers also worked as well. So I guess from the description from the manual, it means only literally the Wipe/wash function as when the washers were activated the wipers didn't wipe. The power seats are working too without this relay, so it looks like that is now ruled out as well as the other circuits that fuse#2 feeds. However as expected, the turn indicators and the hazard warning lights don't work without this relay. What was unexpected, as it isn't listed in my manual is that the rear screen heater doesn't work without this relay either.

So I suppose I will have to keep my fingers crossed and try again after replacing the relay and hope that this is the equivalent to Steve's reset of the module on a 124. Otherwise, I am not sure where to go next if that fails, as all of the circuits that are currently not energised without this relay, all seem to work perfectly with it (except for the fact it drains my battery with this intermittent current draw)

Anyone any ideas where to look next? or should I just buy a new relay and hope that it's the relay itself?

Cheers,
Vance.

----- Original Message ----- 
From: "Steve Nervig" <dakota at mac.com>
To: "Vance Rowley" <vance.rowley at tiscali.co.uk>; "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
Sent: Sunday, March 12, 2006 5:54 PM
Subject: Re: [W126 Coupe] Long term Battery drain problem


> 
> Well, Vance, I can relate to your frustration, because I've had a  
> similar problem with my W124 coupe for about 5 months. Battery drains  
> after about three days of sitting. We may have found it just this  
> week, and your mention of the comfort circuit caught my attention.
> 
> On the 124, there is a comfort module, N52, sometimes called the  
> convenience module. It's a relay that ties into a multitude of  
> different systems, including seats, belt extenders, overhead lights,  
> etc. On my car it is located underneath the left rear seat bottom. It  
> has five different connectors going to it.
> 
> We disconnected it and reconnected it, and it seems to have stopped  
> the drain, although I am not positive. My indy's theory is that some  
> of these electronic modules will sometimes reset if you disconnect  
> them. Don't know if that is a valid theory, but I know of one other  
> case (also a 124) where the same type of battery drain was happening,  
> and disconnecting and reconnecting the comfort module fixed it.
> 
> You didn't mention what year and car you have.
> 
> But in looking in the 126 manual I didn't find a similar module/ 
> relay, so I don't know if this scenario applies to your car or not.  
> But I thought I'd mention it.
> 
> Regards,
> Steve Nervig
> 1992 300CE Sportline
> 
> --
> If you don't know where you're going,
> any road will do.
> 
>
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