I have a 92 400SE W140 that yesterday the Central Locking System stopped working. I first checked the fuses in the rear of the car and discovered the fuse (F4 # 9 20amp) had blown. What is interesting F4 # 9 specifically controls the “closing assist” function while F4 #3 fuse controls central locking, closing assist, and the PSE control module. I replaced the blow fuse and the central locking system worked for a few minutes before the fuse burned out again. I could hear the PSE pump under the rear seat running when I attempted to activate the central locking system. I replaced the blow fuse again (F4 # 9) but now the PSE pump does not run. I you attempt to use the Central Locking System, you will only hear a single, faint click noise coming from the PSE pump – no motor running. The door and trunk Closing Assist work fine, but none of the PSE controlled modules work.

Since the PSE only makes a faint, single click noise, is the PSE blown and needs to be replaced? Does anyone know why the fuse was blown on F4#3 for closing assist when the PSE pump (PSE is controlled by F4 #9) is not controlled by this fuse?

I also checked the vacuum lines that connect to the PSE pump and all connecting lines with the exception of 3 will hold a vacuum without loosing pressure. Do you think these 3 lines caused the PSE pump to fail due to overwork?

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