As far as I can tell, my car does not have power locks. Have I just not found the right button? Especially where is the trunk button located?

Your car has pneumatic central locks. With the key off locking either of the front doors should lock all the doors, the trunk lid, and the fuel door. Unlocking either of these doors will unlock the whole car. With the key on the passenger door will only unlock the car, but the driver's door will still lock it.

The trunk button is below the trunk. With the car unlocked you can press it to open the lid. On my 91 the trunk lock will also lock and unlock the whole car. I don't know if your 81 would have that feature.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

I've never heard of a trunk button on the inside of a benz this old.

Have you never opened your trunk before?

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

To lock all doors, either push down the drivers door lock handle and the rest should follow if the system is functional. To unlock, pull it up again and the others will follow.

The trunk has a real door latch, so to speak, instead of one of these silly new ones that you just have to slam and hope. Just push the button right below the trunk itself, it'll unlatch, and lift the trunk open. There's no automatic "pop open"... you just have to open it like a door.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

That is fantastic! My backseat is no longer my trunk, but my trunk is my trunk! Next question: Why do neither of my keys turn in the driver door lock? Vacuum problem or aftermarket tumbler problem? Anybody?

tumbler problem or wrong key. in 1981, the 126's door locks were only actuated from the drivers door, not the passenger door or trunk lock, that didnt start untill the 1986 MY.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

You should have two black plastic clad keys. The square plastic opens the door and the trunk. The round plastic does not open the trunk; it is for the parking attendant.

Ahh didn't know that! Another reason to buy a post 86 W126!

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Both of my keys are square and at this point I'm more concerned about getting the windows to roll down, the gas gauge to work, and the odometer to work (I'ver read the tips, no it's time to try them!). Thanks again for your help!

I don't know when Mercedes started this, but the trunk can also be locked with the key such that the vacuum system will not unlock it. This enables you to leave the car unlocked for whatever reason while locking valuables in the trunk or to give the valet key to someone while keeping them out of the trunk.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Yeah I'm pretty sure my SDL can do that. I think of I leave the keyhole in the horizontal position the doors will unlock but not the trunk.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

That works for the W123 as well.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.