Purchased an 85 300SD last weekend. Was handed three keys. Two where said to operate the ignition and the third (star-marked) was to open the doors. At the point I knew that the former owner(s) at one point had the ignition tumbler replaced. In testing operation of car I discovered that the one star-marked key would not even go into the door opening of the driver side door lock but the ignition keys would. Thought that was strange. Further testing showed that using the star-marked key would lock and unlock the passenger door and all the other door locks either locked/unlocked from the passenger door. This was a relief for now the pump works for and all door locks operate correctly, just the drivers door lock has issues.
Question is, I need some suggestions on how to make the driver door work. The dealer idea is probably out of the question for they want the whole car to come in. Another possibility is to remove the door locking mechanism and take it to a locksmith. Any forum members have a better idea's.........?

I have a similar problem with my trunk lock. when the tip of the key wears to a slight taper it will bind on the wafers in the lock so that the key will not go into the lock. A new unworn key works fine. A replacement key may solve your problem.

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Gary
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1983 300SD

Does it look as if there is any foreign stuff crammed into the lock?

If you can get the little tube on the WD-40 spray into the Key opening hose it out with WD-40 give it a try again.

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84 300D, 82 Volvo 244Gl Diesel

Load it with LockEase walk away try it next day.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thank you gentlemen helpful comments. I've actually done both and I'll wait and check it tomorrow. When it's daylight tomorrow I'll attach a pic to this thread. The key slot seems to be titled at about a 2 degree angle like someone tried to jimmy this lock. Also, just for giggles I called the dealer asking what a new door handle would cost. Seems it's a little on the pricey side at $495...... so that's not an option.

$495 ? Outrageous! Oh well. If the tumbler is removable like the 300D, then inquire about a door tumbler associated to your vin number. Remove the handle and investigate the tumbler. Maybe it was reinstalled wrong...

Sent from my Nexus 7 using Tapatalk

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

If the lock tumblers come out you could swap the right side tumbler that the key works in with the left side tumbler. And at the same time you are looking for parts that are damaged.
I think you will eventually need to pull the left side and take a look anyway.

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84 300D, 82 Volvo 244Gl Diesel

Pics of key and door lock. In the side profile with the key in the door, I've have wiggled this around and it still will not go all the way in.

Attached Thumbnails

     

I had the drivers door lock tumbler seize up on my 85. New lock sets were expensive. I bought a $20 remote locking kit from amazon that worked with pneumatic locks. Took an hour or so to install. In the 1985 and above w126 cars, its a really easy install.

If I needed to get in with the key I used a different door, but honestly, that only came up if the battery died. The remote locking were a great upgrade and they saved me money.

Take the door handle off the car. Bring it to a mom and pop locksmith shop with the key you want and they can make it work. I didn’t quite understand your description of which key worked on what but basically if you pull out every lock and give the locksmith a key he can make the key work on every lock. This will be way cheaper than the dealer.

Your core looks a bit deformed. Is the little weather door in the keyway? Perhaps it came loose. Can you slide a feeler wire in there to see if the keyway is obstructed like 911 suggested?

Last year I got my blue 300d with three keys. The passenger door, trunk and glove box had one. The drivers door had another, and then the ignition had another.

There were two stock steel keys with the car that matched the trunk, glove box and passenger door. I removed and tore down the ignition lock and the drivers side lock and made the steel keys work in those. My lock smithing experience was a correspondence course from Foley Belsaw when I was a teenager. It isn’t rocket science. If you can adjust valves you can rekey. The hardest part is getting the cores out on the bench.

Check out my Got a 300D thread for some discussion of the lock rebuild.

Got a 1985 300D turbo

Post #33 is the rekeying.

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

dude99, I like your idea and ykobayashi I will do just that and take the mechanism to a local locksmith and have the tumbler fixed. I'm also going to get two new keys for this car, but I need the title in my name before the dealer is going to cut new ones. I assume the star-marked key is original and I want to replace them for my own satisfaction.

Dude99, can you supply a link to one that you've found to work. I'll incorporate this also and it will give the car a more modern appearance.

The unit purchased is no longer available but I'll link it here:
https://www.amazon.ca/gp/product/B0089HRTCI/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Basically you just need to find one that supports pneumatic or air locking. I did a quick search on amazon and this unit specifies in the circuit diagram that you can select Electric or pneumatic locks.
https://www.amazon.ca/AUTOUTLET-Universal-Keyless-Vehicle-Controllers/dp/B07C7XBT8L/ref=sr_1_fkmr0_2?crid=2MDQATVKYF4CY&keywords=car+keyless+entry+pnumatic&qid=1574903566&sprefix=car+keyless+%2Caps%2C202&sr=8-2-fkmr0

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

That's what I did. I didn't want to beat up the passenger door lock by using it repeatedly. I need to save that one in case of dead battery, as you mention. I really ought to take the cylinder out and have it looked at.

Oddly enough, the trunk lock on my recently aquired 300D behave similarly, like someone had jammed a half inch steel rod down inside. I took it out and took it to the locksmith - he tried to clean it out, then his boss walked in and said 'oh hey, that's a valet key.' He cut a the same pattern on the right blank it works all the locks. The valet key has a fatter steel part in the middle. Probably not pertinent to the driver door issue we both have, but who knows.

Valet key on right.

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1986 300SDL, 362K
1984 300D, 138K

Thanks Guys for all the help. To remove the lock assembly on the 126 is not as easy as that of the 123. From talking with a few MB mechanics have been told that some parts will brake is removing the handle and lock assembly. If that happens you need the new on from Mercedes. As much as I like the stealership I'm Not going there........ The next best option is the one about the wireless lock option. I like this one and already planned to install one in a few weeks.

I have an 84 and 85SD. The locks on the 85 are unmolested and the key works all locks.

That same key also works 1 of the doors on the 84 but not the ignition. I read somewhere that there were only a few door locks and that it is common for 1 key to open multipule cars.

I have several keys that open the driver's door on both cars. I replaced the ignition lock on the 84 with a cheap aftermarket lock because there was only 1 key for the ignition and I was afraid of losing the 1 key. Removing the ignition lock is easy if you have a key but a pita when you don't.

The negative of the aftermarket locks is that they are reported to fail early and the local hardware stores couldn't find a blank to make copies. The aftermarket keys have a standard edge cut unlike the OE keys. Perhaps a locksmith would be able to match the blank but I haven't explored because it isn't at the top of the list.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.