Add On Electric Vacuum Pump for W123 Locking System

[Diesel911]

The reason for adding the Electric Vacuum Pump to my Locking system is that the Locking System has Vacuum Leaks and I disconnected it from the normal Vacuum source.
Before disconnecting the Vacuum I installed a crude Trunk Cable Puller to open the Trunk.

Using the Locks manually and using the Pull Cable to open the Trunk all seems OK except that my Wife often leaves the Car and Trunk or both unlocked. I just cannot rely on Her to lock the Car all of the time.

The Vacuum Pump was bought on eBay for previous project and is for a Saab or Volvo; used are in the $55-$75 range.

The Vac Pump does not ground though the Pump Body so wiring is straight forward; one wire is Positive to go to the Battery and the other is the Ground.
I did not mount the Pump on any Bracket if kind of fits into a pocket under the Fuse Box with the Fender Well in front of it.

I ran the Ground Wire through the Fire Wall Grommet where other wires are.


Removed the Hood Pull Lever and then the Plastic side molding on the lower driver’s side. That Molding attaches to part of the Plastic Floor Molding and I had to pull up the Floor mats and remove one Screw that holds the Molding to the floor.


I removed the Plastic Molding because at that point I did not know where I was going to drill the Hole for the Door Switch I was going to add.
After finding a suitable spot on the front Door Frame for the Door Switch I drilled and taped the Hole.

I ran the Ground Wire to the Switch that has little ears you can crimp over to attach the wire and screwed the Switch into the Door Frame. You need to screw the Switch all the way in and then back it out a little at a time until it is adjusted properly so it shuts off when the Door is closed but does not damage anything.

So I tested it out and it works. But, then I realized that if I had to do something that required the Door to be open I would have to disconnect the Wire from the Battery each time.

So I added a Toggle Switch in the Circuit next to the Vacuum Pump. After testing that I realized that I would have been better off with the Switch inside instead of under the Hood.

For the time being I am leaving things as they are until I find a suitable place to mount a Switch inside the Car. Not, in a hurry on that.
It works fine with the only issue being that while it takes little time to build up enough vacuum to unlock all of the Doors and Trunk it takes longer to build up enough Vacuum to lock the Doors and Trunk. (Perhaps my Unlocking System is where the Vacuum leak is.)

The easiest way to live with it is when you are in the Car and the Engine is still running pop the Door open enough to start the Vacuum Pump to let Vacuum build up and simply remain seated a bit. Turn the Engine off and get out of the Car and lock the Car.

The all Metal Door Switch is the one I added.