This car is a 1993 Mercedes Benz 300E 2.8 with a factory alarm when I close the doors with the key in the door key cylinder they lock but after 25 seconds the doors unlock by themselves.The factory alarm is still active because I open the door and the horn goes off. I turn the car on and lock the doors by pushing the lock down and they lock but after 20 to 25 seconds they unlock by itself. The car does not have a door lock/unlock switch inside or an aftermarket alarm. Has anyone encounter this on this cars, could it be the vacuum pump is going bad or it might have a vacuum hose leak? The owner does not have the factory remotes.Thanks in advance.
vacuum leak would not allow the doorlocks to move at all. Most likely has a defective key switch. On this car, you should be able to lock and unlock all the doors from any keyhole. doors and trunk. do these all operate OK?
| Power Lock | blue or green | E | either kick panel |
| Power Unlock | blue or green | E | |
| Notes: Blue wire located in 1/4'' blk rubber tube with RED / wht and brown wires coming out of drivers door. Passenger side same except trigger wire is green. Pump located under rear seat on passenger side. |
If I remember right these will activate by 12v on the green wire, interupt will do the opposite. Basically you have an electrical problem or bad switch as stated above, something is telling the doors to unlock.
An option is to repace all the actuators with aftermarket, using a "central locking" on the drivers and passenger doors to control the backs as well. If you can do the install yourself it will not be that expensive. Add to this a remote keyless entry module and you can integrate it into the factory security system, or use an aftermarket security or alarm/remote start combo system.
Basically on these cars aside from the problem you have, the vacuum lines tend to crack and leak in time, and one by one the door locks get weak and then stop working altogether. If the pump goes you lose all the locks at once. I do this often in this case and this way at least you have a warranty.
Now the locks will move faster then with the vacuum which I prefer, but some people like the slower, quieter operation with the vacuum. But it could be an expensive repair, just paying someone to troubleshoot a benz is steep (well I am sure you know this anyhow).
The only other hope is someone else here is familiar with this particular problem and has an easy fix, but I doubt it. However, if someone does know ...chances are they are a member here..
Good Luck
-------------