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Mike, Mercedes Technician
Category: Mercedes
Satisfied Customers: 39198
Experience:  Tech Expert
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CLK 230K Electrical / Ignition

Customer Question

Hi, I've had a series if problems recently. Some seem trivial but I'll detail all just in case they are relevant. First, the car went dead and wouldn't start. We wondered if this was due to having lights left on.. jumped it and all seemed ok. Once in a while we got the problem where the car wouldn't shift up from first gear (automatic). We pulled over, restarted it, and it resumed normal operation. More recently, the headlights both seemed to blow, one after the other, and we replaced them both. All seemed ok. Then another problem with needing a jump start. Noticed the radio now won't turn on. A week or so ago, there were a series of problems together. The windows wouldn't go all the way up without jolting / stopping. The indicators wouldn't work etc. A guy who deals with electrics locally said it may be something to do with the N10. He gave it a wiggle and all seemed ok again. We're starting to notice problems every time it rains though - the BAS lights come on regularly. I now can't start the car. It's raining heavily and a few minutes ago the HORN started to sound. Then it did it again... then it stopped. Going into the car I discovered the horn no longer works. Looked through the fuses and found fuse 40 blown. Replaced it. The rest of the fuses look ok. The modules look seated ok, and dry. The cable leading into the module box looks damp. Horn still doesn't work though. What's worse is the car now won't start - I'm unable to turn the key in the ignition. Emergency lights work. Windows work. Headlights work. What's causing all these issues to pop up? Is the rain in any way related to the problem I'm having now / is there somewhere I need to check for a leak, or am I missing something else? Help please - need to know whats going on and how to fix it.


NOTE: the remote control WILL lock and unlock the doors. The key won't turn though. I've also tried the spare with the same results, though one of the keys was temperamental and didn't seem to unlock the doors until after I'd tried using it in the ignition. That one might just be a bit flat.

Submitted: 4 years ago.
Category: Mercedes
Expert:  Mike replied 4 years ago.
Hello and Welcome -

My name isXXXXX happy to help you...

Can I just ask - how long has this been going on.... did it have a definate start date / time? Was it after any work done on the car etc?

Too - what is the general condition of the car / wiring etc?

Have you has any proper tests / test equipment / work done on the car to check the circuits / modules etc?

What is the mileage ? and what is its general service / recent repair history?

Do you get any fault lights on at all - on the dash?

Please also give me the Full reg number of the vehicle -

The more you can tell me , to inc the answers to the above, the better -

Rgds, MIKE.....................................

Customer: replied 4 years ago.

The problems first mentioned.. maybe a month or two - the gear shift thing more often recently but perhaps once a week at most.


UPDATE: Just managed to start the car. Left it an hour or so, popped key in and pulled it out fast. Heard a "lock/unlock" sort of clicky noise. Tried the key and it turned this time.


The "Engine" light in the bottom right corner is lit up once I start the engine.


Cars 2001. Seems generally very good condition considering.


No "proper tests" - no. Had the car about 9 months now. Previously had a clean service record and well kept. No problems indicated.


Reg: LN51 WXZ


EDIT: Looks like the horn still isn't working. The BAS or ABS light whatever it was isn't on, but the Engine light remains on.



Customer: replied 4 years ago.
Relist: Other.
I have no had an answer yet - just a request for more information.
Expert:  Mike replied 4 years ago.
Hello again Simon -

Im sorry for the delay - Just to explain -- Im afraid when you re list a question - which you did just 36mins later - before I had chance to get back to you - I lose track of the question...hence the delay - I have just happened across it again.. So please dont re list as it does cause these problems - I wil always get back to you as soon as I can do so -

Now - your problems here Simon could very well be all related - electrically / electronically - because even the transmission on this is electronically controlled...

Specifically I'll just mention, there is a known fault with these transmission wise - and that is a known fault where by the wrong fluid or leak of fluid in the trans, will cause problems as you describe re the shifting - so - I mention that for you to bear in mind...

IF its not that - we 'll tie ion the rest of your issues now... Looking at the electrical system - you could well have all these issues , down to a poor / old or faulty battery for a start... batteries when they are old sulphate inside and while they will tend to look ok - inside they are not retaining full charge - and that in itself will cause these issues - all of them in fact...,. because the systems rely so heavily on the power going through them. So again, a low / faulty or old battery is one problem... The wiring / connections etc to the battery (inc the looms ) should be very carefully checked for bad connections -and any damage anywhere - again - any of which can cause these issues you have - including, low charge to the battery - and high resistance in the circuits - which will cause such issues...

So that needs checking - and ideally, the battery should be pro tested at a garage with pro be sure of its condition... Replace if showing to be old / worn/ faulty etc... and you may in that case, find all well again.

Too though - the charge system / circuit should be checked... It needs to be seen that the alternator is putting out a proper, regular charge within spec ( ie, 14.6 volts )...If its found to be 12v or less or 14.9 v or higher, the alternator / circuit is suspect and then that should all be checked - Again - any such issues will cause what you have for sure.. Any such issues cause problems with the modules on the car. To - do be sure to check the main earth circuit and other earth connections in the engine bay / battery circuit..

Further, you mention the issue with the key - and how you got it started. This can be all down to the above - and certainly before replacing any relays / modules etc , such as the Ign module , the above needs to be checked out first...and then go from there as found..

If all checks out as ok, then progress should be made by way of checking the wiring looms and connections to the various modules - Check too for rain water / damp in any of the fuse / relay boxes inc inside the car... as this is a common issue that can and will cause all manner of odd issues electrically.

If all else is ruled out as above, I would at least at this point, suspect the ign module as the cause of your fault - but there is as you say, the engine management light on. Now while any of the above can cause this - if it remains on after if all the above is proven ok, then you need to have the car "code read" - This is to scan the computers on the car for fault codes. As the EML is on as above - you will have stored fault codes - and these will direct you as to the cause of your faults then - For this of course you will need garage help - as they have the equipment that plugs into the cars socket to scan / retrieve these fault codes.... and then go from there...

So , I have gone through it all in order for you Simon so as to give you the complete overview and save you time - Working through as above you will get to the bottom of these issues you have for sure... Let me know how you get on. Im always happy to help if needed at all more so..

Kind Rgds - MIKE.

.................Please do click on the "OK/ Excellent ratings" for me as that's how Im credited for helping you - Thank you in advance for that...

.....You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Rgds, MIKE.