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Discussion Starter #1
Hello,
My mid-2003 CLK320 failed to start some weeks ago. After recharging and a new battery, I continued getting a flat battery.
Took it to local garage who found that when car was at-rest (not started) the Alternator was drawing 1.5A. Apparently when Alternators go wrong, this is a common fault.
Anyhow, I have a new Alternator fitted and garage have returned car to me, stating that it now only draws 0.3A at rest - I have checked and this is the case.
However many Youtube / general forum advice suggest a car should be drawing a maximum of 0.15 - 0.2A at rest. Of course the garage are happy to continue analysis, but for £75/hr....!
I have a multimeter so I guess I should see for myself and purchase a fuse analyser like this one:
Car Fuse Adaptor Lead Set : Test Leads & Accessories : Maplin Electronics
Question - does the CLK use "blade type fuse holder", i.e. is this the item that I need to check my fuses...?
The garage checked the front seat motors first, as they said these often fail, but they were fine. I also read that the siren is another culprit? Any others to check?

Finally - before I go at it - can another CLK owner let me know if 0.3A is actually reasonable? The reason I figure this is too high, is that on my 100Ah battery, that equates to 333 hours on standby - which is only 2-weeks. I once left my CLK (two years ago) for 3-months and it started fine. Indicating that is could have only been drawing ~0. 05A at the time?
 

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0.3amps is 3.75 watts. A typical indicator LED draws about 1/2 watt. Given that the car has several LED's on (trunk escape button, alarm indicator), plus the electronics that monitor the RCL and DAS systems, 0.3A isn't unreasonable.
 

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Where did you check this 0.3A? At the battery terminals?

I'm going to disagree with rudeney here....0.3A is 300 mA, which is far too high for a continuous current drain when the ignition is off.

For example, some numbers from my WIS (varies on models) on this topic, are listed in the drawing below. Nothing would add up to 300mA!

As stated in the WIS, do the check with the ignition off and all the doors closed (where possible - some fuses are inside the car!)

I would start by pulling fuses on the 'systems' known to have memories, and if nothing there is wrong then move onto other systems. Remove the blade fuse and put the test meter (on the DC mA range) in place of the fuse to measure the drain. You can find out which way the current passes by initially using a higher current range to start with - then switch to the low mA range for the test. Of course, after removing fuses, you may have to 'normalise' the windows, sunroof, etc, to get your saved settings back.

I think that I might have a 'drain' problem with my own CLK, which I just workaround. Just after I bought the car in 2006, the battery was found to be too low to start the car after being parked for just 3 days. After some enquiries at my MB dealership, it was suggested that I tried removing the CD in the Sat Nav section of my COMAND after every use. To my surprise, and 5 years later - no more current drain problems. I have never investigated this issue further - I simply remove the disc after every use.

The fuses your car uses are blade type, available everywhere, with colors to show the individual fuse rating. They look like this. The advantage here is that you can see clearly when the link is blown - this one is shown with protective sleeves over the blades, which must be removed before use.
 

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Discussion Starter #4
Issue continues

Well, after spending £500 ($750) on a new alternator and fitting, my battery problems continue.
I need to buy a multimeter, so cannot do checks just yet (I borrowed one last time) but I sat in car and turned it off. I can hear a whirring noise, like a small motor, coming from between the radio/CD/tv/nav console and the climate control unit. Using my ear alone, I cannot isolate if it is coming from the console or climate control - but it continues for as long as I have ben patient enough to stay in the car (15-mins). The noise sounds substantial enough to be 0.3A if not more.
I have tried removing the NAV CD from the unit, but it still occurs. I have listened to the whirring noise, with both door locked and unlocked - but it continues.
Is there a reset that can be done? I guess I need to confirm this with a multimeter, or stump up yet more cash with Mercedes garage.
This is a nightmare.
Thank you for the two replies - greatly appreciated.
 

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magpie - please complete your profile with UserCP as model/year/location often helps with answers. It seems to me that you are in the UK.

You really do need your own digital voltmeter (for checking all sorts of electrical problems, + batteries in TV remotes, etc.) Maplins sell a digital multimeter for about £15 that would do this job easily. That adaptor looks useful, but you can manage without that.

In my W209 CLK the a/c system sometimes does run on for a brief period after switch off, re-setting all the flaps back to their default positions. This makes a hum - but only for about 30 seconds.

Have you opened the hood to check if the engine fan (M4/7) or the Electric Air Pump (M33) are running after switch-off?

The first fuse to pull would be the one that supplies the a/c system (N22). That is f41 in the interior fusebox. Try that and see what happens.:thumbsup:
 

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Discussion Starter #6
Isolated humming.

OK, I have isolated problem. Sound was coming from between CD/Nav/Radio unit and Climate Control unit. I have isolated 'humming' when car off, to the CD/Nav/Radio unit.

I have found somebody else with EXACT same issue;
http://www.benzworld.org/forums/w203-c-class/1564853-battery-drain-not-seat-modules-satnav.html#post5005681

I know how to get to fuse 64 and have purchased a multimeter to see how much it is drawing. So the question I have (and no doubt henryhb) is is there a way to solve it?

Anybody?

Paul.
 

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Just some additional info:

12V DC power is supplied to the fuseboxes in several categories, ie,

a) circuit 30. This is unswitched battery power (always on)
b) circuit 15R. Powered when ignition sw is in posns 1, 2, 3.
c) circuit 15. Powered when ignition sw is in posns 2, 3.

etc. there are other modes.

Your fuse f64 is fed via circuit 30, so 12V DC is always present there.

Your drain could be a fault on one of the consumers of the supply. Radio, Navigation unit, COMAND control unit. Access to these will be a nightmare - removing all the panels involved.
 

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Your drain could be a fault on one of the consumers of the supply. Radio, Navigation unit, COMAND control unit. Access to these will be a nightmare - removing all the panels involved.
OK, Keyhole disagreed with me on the drain being too high at 300ma, and he's probably right, but I have to disagree about removing the radio being a "nightmare". It's not that bad. There are some good step by step write-ups here (just search), but basically, you remove the panel surrounding the shifter (it's just snapped in place), then the ashtray (plastic clips) then the A/C controls (a few screws) and finally the top button panel above the radio (snapped into place). Then you remove a few more screws and the radio slides right out. I strongly recommend using good plastic trim tools so as not to scratch up things.
 

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magpie

What 'entertainment' features is you car fitted with, eg CD player in glove box, COMAND, Audio 10, Audio 20, telephone, etc? They should all be listed with their 'CODE number' in your decoded VIN - unless you have some non-OEM stuff added later. If that is so, I would suspect that item!

Once that is determined, a circuit diagram would enable you to disconnect cables in sequence, (eg, the cable to the speakers) to allow you to eliminate suspect systems causing your fault.

You must nail this problem, otherwise you will never know if your car will start when youi have parked it for a while....:eek:
 
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