ARGH! Can't find battery drain on CLK - any advice please!!!

[mattman]

Hope you guys can help with some suggestions as this is driving me mad.
My wife has a 2001 CLK Cab 200k with a battery drain (somewhere!) - Its had 3 batteries in the last 2 years, and been into 4 different mechanics and the RAC - they've removed the bulb from the boot as the lenses had melted slightly and they thought it could be staying on when the boot was shut, the latest "fix" was to replace the positive connection which goes through the bulk head has this had corroded and looked to be causing resistance.

I know these sort of things are a bugger to trace, so I haven't got any problems with what's been tried before, but the car is now draining the battery within 48hrs so I'm afraid if I keep jump starting it I'm going to fry the ECU.
I bought a solar trickle charger, but that doesn't seem to make any difference. We also make sure the radio and fan etc are all turned off before removing the key ( i know they should go off anyway but thats how paranoid I'm getting!)

Has anyone had a similar problem, or suggest anything else I can check/replace etc?

Thanks in advance
Matt

[traser]

Hi,

Mine did that, it turned out that what was actually causing mine to drain was the alam siren. It was constantly sounding but was dead so no sound was emitting and no lights flashing. All in all it was about £60 to replace minus labour.

[mattman]

Thanks Traser - not heard of that before - how did they find out that was the problem? will check to see if you can easily disconnect the siren - but guess it won't be simple

[traser]

I noticed a problem with the alarm one day where I came back to the car the hazards were flashing. After trying to start the car it had a flat battery. Mobilo came out and diagnosed a fault with the alarm siren in the computer, which meant the alarm was constantly going, though silently. The guy said it must have got water inside...

I would assume that Mercedes have pulled all your fault codes, if any, and would have found this if it was the case.

[steve_amv8]

Did you have it from new? If not, has it got Tracker installed and you just don't know about it?

The reason I ask is that the Tracker Horizon units fitted in 2000/2001 were (apparently) quite a high drain on the battery and Tracker replaced them f.o.c. several years later with a less power-hungry version (they did on my 2000MY Jeep).

You could try contacting Tracker to see if they have record of fitting a unit to the car.

[Remagel2507]

Had this problem on my 2002 E270. Was the rear SAM unit which also caused the alarm to sound constantly and the rear lights to only work when they wanted to.

[SLacKer]

Hi

Do you have Electric seats?

If so then reach under the seat and pull the 3 wire connector that powers them from both driver and passenger see if this stops the drain. The fix is either give MB a fortune for the seat controllers (which are faulty by design) or cut the permanent 12v and choc block it to the ignition controlled wire (the third is earth).

The seat controller fails to turn off and draws around 700mA per side so if both are going you get a 1.4A drain for no good reason.

Hope this helps. I can give you more info on the fix if you need it.

The other culprit is the fan in the overhead console (where the map light is) this draws internal air across a sensor (i think) and this is known to continue as well, turn off ignition and listen for it.

Edited by SLacKer on Thursday 11th February 17:12

[smashedV8]

Some good ideas above, alarm sirens are pretty common on the clk due to water ingress. In fairness it could be anything.

Surely trying to diagnose the drain properly may initialy be time consuming but in the long term save you time, money and fix it.

Dont want to teach you to 'suck eggs' but do you know the basic priciples of tracing a drain, can talk you through it if not.

As i said its time consuming but not to difficult, and you will be all over the car start by pulling the fuses in each SAM.
Good luck!

Edited by smashedV8 on Thursday 11th February 19:30

Edited by smashedV8 on Thursday 11th February 19:31

[SLacKer]

Following up on Smashedv8 fuse checking idea Maplin do a couple of products that can help

http://maplin.co.uk/Module.aspx?ModuleNo=217881



or if u don't have a multimeter

http://maplin.co.uk/Module.aspx?ModuleNo=217879



The other thing to say is that some modules will power down when the fuse is pulled and not power up again when you insert this test probe so u should be prepared to turn the ignition on and off again whilst these are connected. Remember that the car runs on a few electronic boxes and a comms bus and isn't always a simple 12v wire connects to ground via some light, alarm etc.

[mattman]

Thanks for all the advice guys - after a trip to bristol and back with the renewed battery connection all was going well until this morning. Last used the car Saturday morning - dead Monday morning - just enough juice to unlock the doors, but dead. So going back to the garage to see whats what - will ask them to check out the seats as it does have electric versions. To be honest, I'm an electrical numpty! I can service a car (or used to be able to) change brake pads and bulbs etc, but much past that is a bit of a mystery!

Thanks again
Matt

[Remagel2507]

Oh jus looked through my history and realised that I also changed the battery control module at the same time as the SAM unit as it came up on the diagnostics. Dont know if your car has one but I have also changed the small bike like battery under the bonnet.

[Aspire14]

http://www.pistonheads.com/gassing/imgs/12.gif Hi yah!! Have you had the alternator output checked, it could be that this is not producing sufficient charge (14.4v max)With any kind of short circuit where there is a large flash/spark a fuse would have probably not been able to survive. Check around the starter cables/terminals. Chafed wires could be the cause. Hope you resolve the issue.