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*Premium Member
2008 SLK55 AMG
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1,569 Posts
Discussion Starter · #1 ·
Few months ago i pulled up on my drive returning from work [17 miles one way]. Parked up, switched off, opened garage came back and turned the key, nothing. Once more and started. Thought nothing of it, until it happened another day. Both days no problem on cold starting.

One day came back in from work. Started to go to sons school for parents evening. Required 2 cranks to start. Needed 2 cranks to start on way back as while [5 miles one way]

So as the battery is over 10 years, changed it along with some other MOT related work. Car was sat at garage for 2 days before i picked it up. Came back home, parked in garage. Next day morning, one key turn - nothing, but started next time. So trickle charged overnight and since then been fine for 2 weeks.

Was off work last week but car was trickle charged twice over the week to full charge. Today morning, started fine, went to work with airscarf on and parked up, needed to start the car again to move it a bit, needed to turn the key twice to start. No problem on returning home. Left it out in the cold for few hours, started first time to move into garage.

Is this a battery charging/alternator issue? I am not sure it is. I have a vague recollection of reading something similar here, but cant find it

Any ideas or suggestions, Gents?
 

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**Registered 2009 SLK200
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5,858 Posts
If you are using your car every few days to up to two weeks etc you should not need to trickle charge car inbetween the runs .

You need to find out if you have a fault with your new battery you have bought first .

I can go months without driving my car and it starts up .

You may have a drain issue or bad cell on battery / starter motor or poss a crank sensor fault ?
Plug in and get codes read .

Look at your battery first even though its new can still be faulty .
 

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*DAS/STAR Premium Member
2005 SLK55 AMG
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4,037 Posts
Check your earth connection, and the one to the engine block ... others have had similar issues and it was down to a loose earth ...

BTW, airscarf and the seat heaters are a pretty big drain on the battery / alternator , so a 17mile run might not be putting much charge back in

Alternatively, you might have a rogue module / ecu somewhere in the car causing a battery drain
 

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*Premium Member
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61 Posts
Start by giving it a good run to fully charge the battery. Sounds like it could be a starter motor problem. The on-board diags (if you've got a reader) will show if it's fully completing the ignition cycle.
 

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*Premium Member
2008 SLK55 AMG
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1,569 Posts
Discussion Starter · #9 ·
No errors found other than low voltage. Tech wonders if my trickle charger is ok, as the battery seems ok. The other possibility is the voltage regulator of the alternator. As my Ctek is now 9 years old and sometimes struggles to scroll through the modes, have ordered a new Ctek and will charge up battery. If issue persists, probably new alternator.
 

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*Registered
2006 SLK280
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257 Posts
I've been living with your exact problem for about 4 months now. Had to get towed a couple of weeks ago as it wouldn't start at all. The shop said there were no codes but cleaned the positive cables from the battery. Worked fine for two days and then the same problem came back.

I have already replaced the alternator, new battery last April, starter, crankshaft position sensor and starter relay with no change in the problem. Very frustrating. I went outside today to move it into the garage so that I could check the ground cable and it wouldn't start.
 

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**Registered 2009 SLK200
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5,858 Posts
No errors found other than low voltage. Tech wonders if my trickle charger is ok, as the battery seems ok. The other possibility is the voltage regulator of the alternator. As my Ctek is now 9 years old and sometimes struggles to scroll through the modes, have ordered a new Ctek and will charge up battery. If issue persists, probably new alternator.

I cant see how you are looking at your ctek as the fault !!??

If you have a flat battery after you say two days you have more serious issues as in a drain .
Or faulty battery or ......

My car has stood for over two months now and i was expecting a totally flat battery .
And yes i was right .

A month stood and it will still start on me .

A car should start on its on battery for a week to two weeks easily when stood .

You cant blame your trickle charger .
You have a drain or device draining your battery or tracker fitted ?
Or possible a faulty cell ?

2 days flat battery somethings not right . :surprise:
 

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*Premium Member
2008 SLK55 AMG
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1,569 Posts
Discussion Starter · #12 ·
No errors found after re testing after a full charge with my new Ctek. Problem happened once but not thereafter. Local MB waived diagnostic fee which was nice. Battery, alternator and all modules check out fine.

Strange one. Yesterday when my son got out of car and closed the passenger door, the window didnt go back up. Opened and closed again, working normally. Not sure if this is related or not.

Anyhow, I will keep driving and see what happens. Not going to do much driving as awaiting a knee operation next week.
 

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*Premium Member
2008 SLK55 AMG
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1,569 Posts
Discussion Starter · #13 ·
I've been living with your exact problem for about 4 months now. Had to get towed a couple of weeks ago as it wouldn't start at all. The shop said there were no codes but cleaned the positive cables from the battery. Worked fine for two days and then the same problem came back.

I have already replaced the alternator, new battery last April, starter, crankshaft position sensor and starter relay with no change in the problem. Very frustrating. I went outside today to move it into the garage so that I could check the ground cable and it wouldn't start.
This is very worrying.
 

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Premium Member 2007 SLK280
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249 Posts
I wonder if your problem is computer related as opposed to mechanical. The reason I say that is that the symptoms point to possible issues with the mechanics (i.e., CPS, alternator, etc) but then you also mentioned a window issue that you experienced briefly. My battery had given up the ghost over the winter and after replacing it I had a few ghosts of my own that eventually settled down once the computer "reset" (for lack of a better word) and one of those issues was the windows. Right after replacing my battery (it had been dead quite some time) my auto-down and auto-up wouldn't work, only keeping the button pressed did the trick, but after a couple of hours everything was back to normal.

I may be way off the mark but I had an extra $0.02 so I'm giving it to you :).
 
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*Registered
2006 SLK280
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257 Posts
I wonder if your problem is computer related as opposed to mechanical. The reason I say that is that the symptoms point to possible issues with the mechanics (i.e., CPS, alternator, etc) but then you also mentioned a window issue that you experienced briefly. My battery had given up the ghost over the winter and after replacing it I had a few ghosts of my own that eventually settled down once the computer "reset" (for lack of a better word) and one of those issues was the windows. Right after replacing my battery (it had been dead quite some time) my auto-down and auto-up wouldn't work, only keeping the button pressed did the trick, but after a couple of hours everything was back to normal.

I may be way off the mark but I had an extra $0.02 so I'm giving it to you :).
I'm beginning to think our problems are either computer or ignition switch related.
 

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*Premium Member
2008 SLK55 AMG
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1,569 Posts
Discussion Starter · #19 ·
The problem has recurred once more. Car was in garage on trickle charger for a few weeks as i was off action due to knee surgery. Started first time and drove to bank with top down. On return didnt crank first time but as usual radio etc came on. Second turn started normally and drove home. Since then multiple starts, no problem.

Booked again at dealer on Monday.
 
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