had a new eis fitted 3 weeks ago due to old one faulty it would not open up central locking after standing all night and key would not turn when cold. Have not started car for 3 weeks car battery is brand new and all remotes OK. Came out this morning to go to work early and would not open, one thing I noticed is the alarm light is not flashing.
Something may be drawing an excessive amount of current from your battery when the car is switched off. There are a number of things that could be doing this. With such a drain and even if the battery is new, 3 weeks without being started or being connected to a battery conditioner is enough time to flatten it. If you don't have excessive drain, I would have thought 3 weeks should be ok.
Have you opened the door with the key blade? Did the alarm sound when you did that?
At the risk of stating the obvious, you need to open the boot with the key blade and get the battery on a charger. If you have a multimeter, it'd be interesting to measure the voltage first. As the car is totally dead, I would imagine it's going to read less than 10v. Hopefully your new battery isn't hosed.
Can you not connect the car to a conditioner when not being used? I use an Optimate.
Easy way of opening the boot on an S-class when the battery is flat (I always found trying to use the blade a finger mangling job).
Open the bonnet, take the lid of the right hand fuse box (Drivers side in the UK).
See the front of the big two, or three fuses, usually 40 amp, or 50 amp?
There is a metal bit sticking out of the fuse, either side at the top.
Get a battery or a starter pack, or a pair of jump leads attached to another car.
Apply the negative to the ground point on or near the suspension turret.
Hold the positive to either one of those metal bits sticking out of the top of the fuse.
There should be enough power running through the system to open the boot.
I have used this method many times when I have been working on the car, and the battery has gone flat, had to do it yesterday because I have been swapping the A/C condensor, and the battery went flat.
Ignore the circles, its someone elses picture, the arrow is pointing to what I am on about.
When I get home from work , will open with key and put computer on it. This is exactly the same issue before I had the new eis. (S55 amg). I sent the old eis away to be repaired but the temperature switch was knackered that's why it would not work in the cold. If I lock the doors without putting on the immobiliser it seems fine, well it was before the new eis went in. £850 and still not solved. The only thing that came up on my diagnostic mb11 was can bus lines interrupted.
When I get home from work , will open with key and put computer on it. This is exactly the same issue before I had the new eis. (S55 amg). I sent the old eis away to be repaired but the temperature switch was knackered that's why it would not work in the cold. If I lock the doors without putting on the immobiliser it seems fine, well it was before the new eis went in. £850 and still not solved. The only thing that came up on my diagnostic mb11 was can bus lines interrupted.
Although you might rue spending on a new EIS, the chances are it would fail eventually anyway. Mine started to play up at 70k miles/15 years old. At least you know now you're not going to have to worry about it any more (and a dodgy EIS can cause lots of weird and annoying problems)
OK, if you have not started the car in 3 weeks the battery will be flat, these things can flatten a battery in less than that, all of the systems running even when the doors are locked sorts that out.
The first thing to do is get into the boot and charge the battery up as Amgeed said.
I have shown you how to get into the boot the easy way, the drivers door can obviously be opened with the blade as Chris said, its easy to open the door with the blade, a lot harder to open the boot because it requires twisting and pressing, not an easy job, especially if you have a thick number plate trim, impossible with my car as it has a reversing camera in the same place as the key.
What temperature switch?
I take it the £850 EIS is a new one from a dealer that has been coded to your car.
If you had this fault with the old switch, replaced it with a new switch, and you still have exactly the same fault, then its a pretty safe bet that the fault isnt in the EIS.
Which diagnosis machine are you using?
Do you have keyless go? Is that affected by temperature?
This is a section from w220.ee concerning the drive authorisation system, there are many more things involved in starting a Mercedes built in the last few decades, this may give you a few pointers.
This is a video about how to test the EIS with a decent diagnostics machine, its doesnt cover not being able to turn the key at all, but when you turn the key, you can test the EIS yourself, it may vary from machine to machine, but can easily be adapted.
I had the same problem a while ago where the key would not turn, it turned out to the the front Pre-fuse (Another why did you design it like that? Mercedes job), I wouldnt suggest you try the pre-fuse yet because
a: Its a PITA to get to
and
b: suggestions are mainly guesswork, and guessing is a damn fine way of emptying your bank account with a Mercedes.
