I recently replaced a seized up ignition switch assembly on my 1985 W123 300D with a boneyard part. I also replaced the electrical rotary switch on the back with a new (Duralast) one. I disabled the steering lock (previous owner had done that to the old one already too, it seems)



It all works, but is stiff. I tried spraying LockEze in there, it helped the key/tumbler operation, but not the rotation of the whole assembly when all put together, which still seems, not like it's catching just like it's too tight.


When I have the rotary electrical switch in the back unscrewed and removed, the cylinder rotates fine. If screw the rotary switch back on, and don't torque it down too much, it's usable but feels stiff. If I torque those 3 screws down too much it won't rotate at all. For now I'm fine with just leaving those 3 screws kind of loose but it kind of bothers me.



I saw some guy on youtube selling some expensive kit with fancy grease but I don't want to go that route.



I called the dealer and asked what they recommend, and they said they don't know.



Is there a non-fancy, ordinary, can-buy-at-any-hardware-store-or-auto-parts-store grease that would be good to lube up the ignition mechanism?


Thanks

__________________
1985 300D, originally California, partially un-California-ized.

Sounds like you are having the same issue I just had with a cheap non Mercedes switch. See post #26.

Jammed ignition lock - steering column mechanism worn

I really had to monkey around with this switch before I got it working. Turns out there was an internal dimension that is off. The switch binds up after you tighten the screws. It needs to be completely disassembled by pushing in the black lock tabs and pulling the switch mechanism out of the housing. Then You need to shim it with three washers inside, between the housing and black switch mechanism.

Note this is not putting washers on the outside. It needs to be taken apart and have the internal clearance shimmed. Then you snap it back together.

That Chinese switch is junk. I will eventually remove it and put in an MB switch I recently ordered once it cools off outside.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Graphite is the best lubricant for the W123 ignition switch. Using a number 2 pencil with graphite lead rub the pencil lead on your key grooves on a regular basis. Also be sure your key chain has very few keys. It has been documented that excessive weight on a W123 key chain will cause problems over time for the ignition switch. Also, make sure your key is made of steel and not brass. The brass key will over time leave brass filings in the switch which are harmful to the switch.

This will work for the cylinder lock tumblers. But OP's problem seemed to be with the rear electrical switch. Teflon lube might work on that. Work it back and forth until it turns freely. I installed one, but never had that problem I think it was OE.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Silicone lube is I believe the preferred lube but no lube will fix gummed up or worn tumbler and steering lock components. A new tumbler key assembly may fix your problem but the solution is a new or rebuilt lock assembly. I was lucky to find a New OEM (MB) on ebay for only 120 bucks. You need to remove the unit from the car and clean and inspect it, not the easiest job. If the unit jams you are SOL.Fix it before it fixes you.

Silicone lube will attract dirt. Not advised.

Dont do what i did , and put gease on the key,,i then pushed it in to the switch as soon as i did it then the starter would not stop working untill i riped off the battery terminals ..