I just purchased an 84 300SD from a mechanic who sold me my 85 300SD almost ten years ago. He had maintained the car for the previous owner for over fifteen years. It replaced a 85 300D that was retired due to rust and a bad transmission.

The 85 SD went over 200,000 miles since purchase without a serious issue. Because of minor oil leaks over time, the ball joints, tie rod ends, motor mounts chassis mounts etc needed replacement. So the mechanic told me he had a "like new (124,000 mile), always garaged, serviced by him for the past several years, etc." Sounded good so I bought it. What a mistake. Nothing but problems from the start of the trip home. I've been able to correct many of them but I have a question on the 84 SD trunk lock, obviously.

The vacuum system controls all of the locks when operated from the driver's door lock. My question is, "Does the trunk lock on the 84 SD also control all of the locks like on a 85 300D and SD? I can feel the lock go past the open position when turning it counter-clockwise to open with the key. I don't want to buy the element if if isn't going to do anything the current element does not do.

Thanks for any advice.

It sounds like you either have a bad element or a vacuum line with a leak.

The fastest and most accurate way to solve a problem on a MB is to use these two links and learn to use the search function on this site. Learning this was stressful to me.

DIY Links by Parts Category - PeachParts Mercedes ShopForum

Mercedes-Benz 126 Service Manual Library

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84 300SD
85 380SE
83 528e
95 318ic

I'm not sure what your question is. Are you unable to open/unlock the trunk?
Yes, the pump in the spare tire well controls the doors, fuel door and trunk locks.

If so, your factory alarm may have locked. These are separate actuators on the 300SD.

There are a couple of ways to go about this. You could reconnect the alarm controller, under the front passengers floorboard. If that doesn't unlock the trunk, let me know and I can send you a PM for a backup procedure.

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Sam

84 300SD 350K+ miles ( Blue Belle )

the way I read the question is...

the trunk locks and unlocks... but the key does not actuate the pump to unlock the rest of the car.

is this normal for the 84?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

If so, that is normal. Only the driver's, and on some the front passengers, door locks have the switch that controls the pump.

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Sam

84 300SD 350K+ miles ( Blue Belle )

My 85 actuates the pump from any lock on the car.

also, all my 124's and 201's do.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

When I checked the wiring diagrams, this was incorporated in 85. In fact, my 84 only unlocks from the driver's door.

Must have been one more of the nice little things they added in the 85 year model.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Thanks SD Blue. It looks like I just wasted some money and time purchasing and to be installed passenger side vacuum element thinking it also controlled all the locks.