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Thread: Door lock issue

  1. #1
    Junior Member
    Join Date
    Aug 2018

    Door lock issue

    Hi all

    Good day. Purchased by 94 E500 back in October, odd issue with vacuum door locks. They will always unlock from trunk or driver's door, but sometimes they do not want to lock. More often I can get them to lock from the trunk, and sometimes I can get them to lock from the driver's door (either with the plunger from inside or with the key outside) but often trying to use the plunger or key leads to just the driver's door locking, without any response from the rest of the system. If I manually lock everything, they will all unlock with the key, so I not think it is an issue with the under rear seat pump. The car does have an aftermarket alarm - not sure if this matters. I am thinking there is something wrong with the driver's door vacuum switch but will appreciate any suggestions.



  2. #2
    Site Honcho
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    gerryvz's Avatar
    Join Date
    Nov 2008
    Annapolis, MD

    Re: Door lock issue

    The fact that the locking is intermittent from both the trunk and driver's door is puzzling. Have you tried the passenger-side front door for locking and unlocking -- does that work as well? Intermittently, or consistently every time as it should?

    Initially, I was thinking that the electrical contact switch in the driver's door (and possibly the trunk) is bad. This switch sends the electrical signal to the pump to activate the locks, when the key is turned. Could be a starting point, but I think the problem lies with the alarm system that was installed after the fact.

    Is the aftermarket alarm tied into the door locks, or is it just a noisemaker that sounds when a door is opened?

    One other question -- of an operational/tactical nature. When you use either front door lock with the key, do the windows go up or down together when you hold the key in the "lock" position (windows should go up and sunroof close) or "unlock" position (windows will go down)?

    My bet is that the aftermarket alarm is the root cause of the problem. I bet it's an older install and the brain box is partially fried. Hopefully you can remove the alarm from the car and set things back to the stock setting.


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