[Jawsplace]

Recently my ‘97 S500 coupe’s central locking started acting up. Red & green lights are working but that’s it - nothing else responds to the key fob. From inside when using the locking switch on the dash again the locks don’t respond, however…pressing the lock switch repeatedly causes the dome light to flash! Very odd.

Even stranger, if I turn on the dome light and then try the door lock switch I hear some something running (sounds like the vacuum pump?). But still the door locks don’t move.

In addition, the window pop-down doesn’t work correctly when opening/closing the doors.

Anyone know what the connection is between central locking system and the dome light circuit?

Desperately wanting to find the culprit!

 

[samosali]

hmmmm, this can be difficult to resolve, however the part which you ask about, so the connection between locking and dome light, is so called PSE pump. It provides pressure and vacuum to locking system (in addition to many other functions). To the best of my knowledge it also affects the dome light but I cannot prove it in this moment, it is just how it stays in my memory ... maybe I am wrong. This pump is under the right rear seat.

 

[Jawsplace]

hmmmm, this can be difficult to resolve, however the part which you ask about, so the connection between locking and dome light, is so called PSE pump. It provides pressure and vacuum to locking system (in addition to many other functions). To the best of my knowledge it also affects the dome light but I cannot prove it in this moment, it is just how it stays in my memory ... maybe I am wrong. This pump is under the right rear seat.

Thanks. Yes I need to start checking the various components in the system, starting with the pump under the seat. I’m also wondering if perhaps there’s a micro switch problem in the door latch (I believe there are two - one for soft close and one for pop-down window).

 

[MAVA]

The motor in in these central locking pumps sometimes short out, and it is possible it can cause a fire / melt down the pump. inspect the pump. It sounds like that. Either have the pump fixed, or unsolder one the motor leads / cut and wire nut cap one of the wires at the motor. You need to remove the bottom cover. Sometimes, the sunroof drains get clogged and the water will run-off into the central locking area, and flood the area where the pump is located. Since the central locking pump circuit board is on the bottom, it can be all wet / shorts out / corroded. You will need to remove the bottom cover of the pump.

Martin