Does anyone with and understanding of diodes and capacitors know why , on the ESL on a W211 and most likely others, there is a small magnet on one arm of the locking pin the moves up and down with the locking pin as it locks and unlocks (moves up and down). As it does it moves across a pair of diodes on the PC board. When it is in the locked position the magnet is next to one diode and when unlocked it is next to the other one.
Does this have something to do with changing the direction of the worm gear / the motor?
Any electrical engineers out there?
This is important to know if you are replacing the ESI circuit board from one ESI with a bad motor to another that is good. This way you don't need to re-program it.
Great fix...cheap....but you need to know the position of the locking pin on both so they match.
Anyone have an idea?

 

Brian you got a few things mixed up... I mean everything is all mixed up: diodes, names... ​​​​​​Let's focuss on solutions. ✌️

These bad Steering Locks can be simply revived with a new electric motor for next to peanuts
-Or
bad ESL can be bypassed with a new emulator module that is programmed to satisfy the car security logic.

The EIS module is also a trouble maker. While working around the steering column, take the opportunity to resolder the loose PCB connections on this module.

 

Cali I appreciate you taking the time to reply. My question was purely academic....I just wanted to know how that magnet affects the diodes, if in fact it does.
Diodes being basically a one way switch (which is the limit of my knowledge of how they function) I wondered if creating a magnetic field near one could change the direction of the flow or perhaps interrupt it completely and change the direction of the motor to lock or unlock the steering.
But on to the possible repair options.
Replacing the electric motor with an inexpensive cheap Chinese one is just inviting a repeat of the present issue.....just sooner than the original motor offered.
The dealer will sell you a new ESL.... but that still requires coding. Apparently, unlike a replacement key, it doesn't arrive programmed....it has to be programmed by the dealer with the car present. How to get the car there presents it's own set of challenges considering it won't start if the ESL is "locked".
They quoted 3.5 hours and some outrage amount of dollars to do it, which is total BS !
So, you could still buy the new ESL from the dealer without taking advantage of their generous offer to program it and simple replace the circuit board in it with the one in your original ESL. It comes out pretty easily and from what I've read it is rarely the cause of the ESL to fail.....unlike some many of the other electronics in late model Benz's.
Presumably the motor in it will be of a better quality than aftermarket and therefore offers a degree of confidence it will last a good while longer than aftermarket.
I don't think I would do this with a used ESL purchased online from eBay or the like for obvious reasons.
An emulator is a great idea but requires removing the EIS and taking it (sending it) with the key to someone who can supply the emulator AND program it. It is pretty expensive considering the process involved. But, it doesn't take 3.5 hours. More like 20 minutes....and that allows for a coffee break.
I know... I know.... they had to purchase the programing tool and download the software, but do they really need to pay for it with two or three jobs?
Anyway, a good option but shipping has it's own worries and expense and takes days to turn around. Could be an issue if you only have the one car.
Alternatively, there seems to be a number of emulators on the market for less than $100 that do not require special equipment to program.
Basically, unlock the ESL, (that is key, it must be unlocked)....remove the plug and plug in the emulator. Cycle the key a couple of times and voila.....it works.
Hopefully it keeps working.
So, those are the choices...the good the bad and the ugly.
Of course....you could always trade it on a Genesis (Hyundai) : )

 

Brian you're really close to selecting a great solution. There are pro & cons associated with each choices.

Personally, I would stay close to the original design by replacing the tiny electric motor and greasing the dry mechanism until smooth!

As far diode sensing they are used as LED in optical sensors to detect positions. Magnetic sensing is achieved with hall sensors in the camshaft and crankshaft position sensors.

 

Sadly people are assuming MBZ replacement parts are 'better quality' than stuff from 'web'. That IS NOT true. Ofter, the replacement part from the Dealer is New Old Stock and 20 years old. I once needed the formed hose connecting the cylinder heads for my 1994 sl-600--as the original had been mis-installed so that it just barely sealed, and when age related shrinkage caused it to leak when HOT. Took forever to locate the leak as it was from the bottom next to head surface only when HOT and was a gradually appearing (slow loss of fluid from reservoir). The replacement part was from 20 year old 240D stock. (which I handed back tt Parts guy.)

 

Yeah....NOS is not always a good thing.