Bob, I tried to send you a pm private message but could not, you may have this feature disabled.

You may find the components of the remote entry system in this area near the pump, don't let this confuse you.

The pump has two electrical connections one rectangular (power and ground as described)

AND one round connector (these wires have either 12 volts Unlock or GROUND CONNECTION lock signal from either front doors and/or trunk lock) Also the vacuum lines go to the pump too.

On your w124 CD, go to disk 1, select model, select Electrical troubleshooting manual, select Wiring diagram, type in page number 143 in the PDF menu bar or go to page 143 see wiring of all door lock components. Follow the power wires in the diagram down to the (vacuum) Supply Pump, also follow the main red/white wire to the front door locks and trunk lock. You can clearly see how turning the key in the lock will send either 12 volts OR ground to the vac pump. You will note that the Anti theft alarm and convenience control unit are also part of this circuit but just follow the lock and unlock components.
Acky

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