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Discussion Starter #1
Something I can't find in a manual is the current draw from the battery when the ignition is completely off.

I suspect I have an excessive current drain which is draining my battery overnight on an '03 R170 SLK. It is stock with no add-ons so current drain should be roughly the same as all other same models

When I disconnect the battery & put a 12V PS on the car leads I see a 1Amp draw quickly dropping to a steady 0.7A draw

This would seem to be excessive as it means a 70amp hour battery would delete in 100 hours. My battery is not drained overnight but depleted enough that car won't start. I reckon the Platinum Prestige Heavy Duty 3 year old battery is probably weak but before i change it any help would be appreciated as putting in a new battery is just a bandaid
 

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Registered 1997 SLK230 Kompressor
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217 Posts
Glove box or trunk/boot lights staying on is a typical cause of excess current draw, although you seem to be heating something up with about 8 watt which is really quite excessive either way. I'm sure someone else will chime in.
 

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Registered 1997 SLK 230
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I think WIS says somewhere that that quiescent current should be around 25ma so your reading is way too high. BTW when you measure it the reading will be initially higher but should drop to a low value as things go to "sleep". On my 230 I had a reading of around 200ma that never dropped any lower. Time to start pulling fuses to try and pinpoint the culprit. In my case it was the internal battery in the alarm siren which was the root cause.

Good luck in finding your issue.

Sent from my SM-T210 using Tapatalk
 

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Discussion Starter #4
Thanks guys - just the info that I needed - even though chasing down the offending circuits will be a problem.

Seems like best way to analyse this high current drain is to keep my 12V PS connected while pulling fuses?

I suspect that it might be on of the rear speed sensors shorting - probably the rubber cup filling with water & shorting across the sensor connector. I have dashboard ABS & lights on for a while now but I knew one of the rear sensors was not working & my garage said it was the wiring that was flooded but - seemingly a common problem (now that I have investigated it)

I examined this sensor but no flooding found there - will try the far side tomorrow.

BTW, I have bought & downloaded the R170 maintenance manual as I reckon I can save myself some money with these type of repairs but I couldn't see from wiring diagram which fuse controls power to speed sensors?

@borris1954 - what is WIS - I presume some works manual?
 

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Premium Member 2001 SLK200K, 2001 SLK320
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I'd go with efair's analysis, they are the usual suspects.

- HERE - .. is a little light reading on the general topic of battery discharge ..
 

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Discussion Starter #8 (Edited)
Thanks guys
@efair - I've already removed the PSE - waterlogged (seems a common problem with SLKs in wet climates?) - but with this removed still the 0.7A current drain
Where do I find the alarm siren - under the bonnet - actually, I've never heard the alarm go off so could be this, indeed?
@M4rCu5 - thanks, I'll have a read

PS. lights flash when alarm set & unset but no beeps - I presume this would come from siren - I bought it second hand so never heard these?
 

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Discussion Starter #10
Thanks @Sneaky Pete - I'll have a read - I'm putting my money on a rogue siren unit, atm - will check it out tomorrow but there seems to be lots of confusion over where that siren unit is located?
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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If you've disconnected the PSE that should be enough - the siren receives its power from the PSE. But just to answer your question - it's under the windshield, and you must remove the wipers to access it.
 

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Premium Member 2001 SLK200K, 2001 SLK320
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PS. lights flash when alarm set & unset but no beeps - I presume this would come from siren - I bought it second hand so never heard these?
Alarm 'beep' or chirp as it's more commonly called is not the default setting. That's 'Dutch' or 'Netherlands Mode' and has to be enabled via SDS or a stealership.
 

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Registered 1997 SLK 230
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215 Posts
Some models (mine for one) did not have the factory alarm but instead had a dealer fitted "Scorpion" alarm such as this:


In my case it wasn't powered from the pse although appears to be connected to it presumably so it knows if the roof is up or down. My siren is mounted on the left hand inner wing.

Keep hunting.

Sent from my SM-T210 using Tapatalk
 

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Discussion Starter #15
Thanks guys - SWMBO says I have to go out today to return some gifts but will test the car later & report results
 

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Discussion Starter #16
Jaysus, one problem after another - before I set off in the car I opened the boot to put some bags in & I thought why not test the boot light to see if it's turning off when boot shuts - so in looking for the switch that trips when the boot is closed I flipped the boot lock closed & now can't close the boot

My car keys won't allow me to twist the lock fully as the big square remote fob that the key is on fouls against the lock surround when twisted

Jeez, I'm just not cut out to be a Mercedes owner
 

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Discussion Starter #17
My key was being blocked by the number plate - a bodged job drilled into the body work & too big so blocking the turning of the key fob

I removed the number plate - the key now turns but nothing opening in the boot lock
My PSE is not working & so is disconnected so I can't release the lock using remote fob

Anybody want to buy a deconstructed SLK?
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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BTW, I have bought & downloaded the R170 maintenance manual as I reckon I can save myself some money with these type of repairs but I couldn't see from wiring diagram which fuse controls power to speed sensors?

@borris1954 - what is WIS - I presume some works manual?
Maintenance manual? Repair manual? I was under the impression those were not OEM but rather knockoffs/copies that are (usually/all) incomplete or defective in some way. @jbanks15 ?
 

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Administrator 2009 SLK 55 AMG/Founding member 2006
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maintenance manual is different from repair manual
 

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Discussion Starter #20 (Edited)
I sorted the boot locking issue - opened up the panel in the boot lid to get access to the locking mechanism
Jeez, everything to do on this SLK requires chasing down rabbit holes of ever decreasing diameter.

PS, Thanks for the like, idiot101 - I'm a fellow traveller dweeb
 
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