W204 would not start . . . . but then it did!

[Fogey]

Hi all

I have a 2011 W204 C Class Estate which has performed faultlessy over nearly 2 years of ownership.

However, yesterday it would not start . . .
The car onlocked on the remote, mirrors powered up and dash lit up as usual. I turned the key to the start position and everything went dead. My first thought was that the battery had died (I assumed that the remote locking, mirrors etc were powered by the auxillary battery in the boot(?) ). The battery however checked out at 12.3 volts. Didn't have time to do anything yesterday but tried to start the car again this morning - still the same - everything appears ok until I turn the key from position 3 to start the engine and nothing - dead as a dodo.

I have Green Flag Home Recovery so gave them a call and they arrived shortly after. Embarrassingly the car started instantly at the first try!!!!!
The recovery mechanic checked for fault codes but there was nothing recorded and could not come up with a definitive reason for the car not starting yesterday

Ideas would be much appreciated.

Many thanks.

 

[Auto-mobile]

If you have a spare key carry it with you and try it the next time it happens.

Failing that it will probably be the steering lock, the zip sound you hear when entering the key and taking it out is the steering lock, if you don't hear it next time then it's your steering lock failing.

 

[Fogey]

Thank you - I did try the spare key yesterday but that didn't work either.
Hadn't considered the steering lock though - is this a common issue and something that can be sorted or is it likely to need replacing?

 

[MancMike]

Sounds like your ESL motor is on it's way out. Read about it, as if you catch it while it's working it's a cheap DIY fix if you're confident. If it fails in the locked position the car is going nowhere and you're looking at many hundreds to replace.

Is this the start of the W204 ignition issue? - MBClub UK - Bringing together Mercedes Enthusiasts

It is a common issue, it'll happen on all of them sooner or later. The motor is just crap. I fixed mine myself and got lucky that it failed on my driveway in the unlocked position.

 

[baxlin]

Might sound daft, but I had this on an older, less complicated car, it was as simple as the battery terminals not having perfect contact, either not tight enough or dirty. There is enough contact for low load, but not enough for heavy starter load.

 

[grober]

IF YOU ARE ON THE ORIGINAL MAIN BATTERY 2011? time possibly for a new one. Its under the heater duct that protrudes into the engine compartment - the duct just clips on.
Lead acid battery voltage is often misunderstood Its not 12 volts . A fully charged battery should read 6 cells x2.2 volts per cell = 13.2 volts. Anything lower than 12.6 denotes a low charge battery

ps I wouldn't discount the ESL warning either mind!

pps I always advocate changing an older battery as amatter of course with todays cars so heavily reliant on electronics . For the price involved its a no brainer.

 

[MancMike]

If it's a flat battery, it'll still normally have enough juice to unlock the ESL when inserting the key. You'll just get a click and nothing else when trying to start.

If it's the ESL fault, everything is normal until you put in the key fob at which point nothing happens, not even the normal sound of the ESL disengaging. THereon, nothing will happen as it'd be dangerous. The ESL has to be in an unlocked state for anything else to happen with the car.

 

[Fogey]

Many thanks to you all for your input
ESL motor failure sounds spot on.
Is the motor available seperate to the complete ESL unit either from MB or elsewhere?

 

[Fogey]

Presumably this is the part . . . . ?
ESL / ELV Car Steering Lock Wheel Motor Mercedes-Benz W204 W207 W212

 

[grober]

Electronic gubbins required as well! quite few traps for the unwary! There will be specialist repairers out there with the necessary kit and experience. Don't think MB will repair em- just fit an exchange unit which will need to be coded to the car?
https://youtu.be/UYsBxxOXoA4
[YOUTUBE HD]UYsBxxOXoA4[/YOUTUBE HD]

 

[MancMike]

Yes that's exactly the part. It just drops right in as a replacement.

I got mine for about 17 quid.

It's critical that it's in the open position to do the repair yourself. Whether it fails or you preempt the failure. If it fails in the locked position it's game over, new module, grinder, star coding, avoid at all cost.

If you are going to diy it, feel free to message me. A few bits are tricky, but I managed it.

 

[Fogey]

Yes that's exactly the part. It just drops right in as a replacement.

I got mine for about 17 quid.

It's critical that it's in the open position to do the repair yourself. Whether it fails or you preempt the failure. If it fails in the locked position it's game over, new module, grinder, star coding, avoid at all cost.

If you are going to diy it, feel free to message me. A few bits are tricky, but I managed it.

Thanks - so diy replacement of the motor is possible without all the gear in the video?

 

[MancMike]

Yes. You're just replacing the motor. It's not a clever motor, just a normal cheap motor with a worm gear on it.

Providing it fails in the unlocked position, or you do the fix while it's working, put the key in, hear it unlock, then disconnect the battery, you can DIY it without any special tools.

The hardest part is getting into the unit. There are pins, you'll need to tap out, or drill out if you can't tap them out, to open the enclosure (there's a tool to do it, but not worth buying if you can just tap them out). You replace the motor and reassemble. When back on the car, with the power restored, the car is none the wiser anything has happened. It's the same board, so no coding required.

To hold the unit closed I used a metal jubilee clip as it'll obviously never fail like electrical tape might.

 

[moonloops]

My W204 did the same, it was a relay in the fuse box. Prior to having it replaced I could tap the fuse box when it failed to start and it would suddenly start.

 

[Fogey]

Yes. You're just replacing the motor. It's not a clever motor, just a normal cheap motor with a worm gear on it.

Providing it fails in the unlocked position, or you do the fix while it's working, put the key in, hear it unlock, then disconnect the battery, you can DIY it without any special tools.

The hardest part is getting into the unit. There are pins, you'll need to tap out, or drill out if you can't tap them out, to open the enclosure (there's a tool to do it, but not worth buying if you can just tap them out). You replace the motor and reassemble. When back on the car, with the power restored, the car is none the wiser anything has happened. It's the same board, so no coding required.

To hold the unit closed I used a metal jubilee clip as it'll obviously never fail like electrical tape might.

That's very helpful and much appreciated - thank you again

 

[bishopstone]

Electronic gubbins required as well! quite few traps for the unwary! There will be specialist repairers out there with the necessary kit and experience. Don't think MB will repair em- just fit an exchange unit which will need to be coded to the car?

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[YOUTUBE HD]UYsBxxOXoA4[/YOUTUBE HD]

I have the problem with a C200 2008 and no help from the normally co-operative main agent. How would I find such a specialist please?

 

[grober]

Hopefully someone in the aylesbury area can advise?

 

[pcthrillrider]

IF YOU ARE ON THE ORIGINAL MAIN BATTERY 2011? time possibly for a new one. Its under the heater duct that protrudes into the engine compartment - the duct just clips on.
Lead acid battery voltage is often misunderstood Its not 12 volts . A fully charged battery should read 6 cells x2.2 volts per cell = 13.2 volts. Anything lower than 12.6 denotes a low charge battery

ps I wouldn't discount the ESL warning either mind!

pps I always advocate changing an older battery as amatter of course with todays cars so heavily reliant on electronics . For the price involved its a no brainer.

lead acid? arent they agm now? mine is

 

[grober]

You are correct most modern car batteries especially those with stop/start are AGM now- however their chemistry is still lead acid based afaik.
https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

 

[190]

Yes they are all lead acid. The differences are in physical construction and whether they are valve regulated.

A "normal" wet cell battery will have a rested fully charged voltage of 12.6 -12.7 volts. An AGM will be up to 13.0 volts or even a touch higher. I have one in my motorcycle which is 13.05 volts.

The practical differences are, AGM batteries generally have more cranking amps and hold their charge for much longer in storage. An AGM will be valve regulated which means it has a safety valve that blows at something like 2 PSI if the battery is overcharged. This is the reason AGM's should not be charged in recondition mode which uses an excessively high charge voltage.