W126 Ignition tumbler replacement

When new, a W126 Mercedes would have come with four keys:

• Two square headed master keys.
• One round headed valet keys.
• A flat ‘wallet’ key.

The master keys were designed for everyday use and opened all locks on the car: doors, ignition, glove box and boot.   The valet key is similar, but does not open the glove box or boot if manually looked.   The premise being you can keep valuables in the car while being parked by a parking attendant.   The master key doesn’t have a plastic head.  Instead, it has a small flat metal one allowing it to be kept as a spare in a wallet.

The wallet key is usually lost over the years.  I’ve owned many of these cars over the years and never had one.   Normally when buying the car used, you get some combination of other keys.    In the case of the 300SE, I received only one original key – the valet key.   The ignition tumbler had been replaced by a generic unit which no longer matched the other keys on the car.

The main problem with this was that should I accidentally lock the keys in the car or loose them, I would loose access to the car.    The simplest option would be to have the valet key copied.   However, that would leave me with two annoyances: two keys for the car, and the inability to open the boot should the central locking fail.     At this point, the simplest solution was to contact the Mercedes-Benz Classic Centre in California! For USD$51, I could get a new ignition tumbler for the car and associated master key.

Changing the tumbler is a simple, but fiddly job.     The key needs to be in the #1 position.   There is a small hole between the black collar and the tumbler where a tiny allen key or micro-screwdriver can be inserted.   This pushes back a spring that allows the collar to be unscrewed.    The collar can’t really be unscrewed by hand because of the trim, but the factory tool is basically a short section of rubber hose the same diameter as the collar.  This tool protects the paint of the collar.   I didn’t have it, and the W126 trim hides the collar pretty well, so I used medium size long nose pliers.

The installation of the new tumbler is a bit more tricky.    The process is the reverse, but I ran into a couple of problems.    I wasted 30 minutes because the small hole on the new tumbler was slightly smaller than the old.   A paper clip fitted but was too weak.   In the end I found a micro-screwdriver that worked.

The tumbler with key attached, collar and ‘tool’ all need to be aligned and then screwed on.   This took a bit of fiddling to align.    Overall, the job took me one hour and I now have a single key for the car, at the expense of about AUD$100 (including shipping) and a few scratches on the black collar.