PeachParts Mercedes-Benz Forum - View Single Post

jay_bob · #7 01-20-2020, 10:14 AM

That sounds like a good theory.

Pump is located beneath the seat in the second row on the right side.

There is a 3 pin connector at the pump with a blue, yellow, and green wire. These are the signals from the door switches.

Blue = driver door
Yellow = tailgate/trunk
Green = passenger door

These are fed from a double throw switch in the lock assembly. It applies +12 to unlock and ground to lock. The pump figures out the signals and does either a vacuum (to lock) or pressure (to unlock). On the 124 there is just one pneumatic circuit for everything (all 4 doors, tailgate/trunk, and fuel door).

On the pump there is also a 3 pin connector with red and brown wires. This is the power for the pump, unswitched power from fuse C. If you have ortho seats the pump will have a 3rd black wire in that connector for the ortho pump feature and a second pneumatic circuit for the seat cushions.

A 94 will have the convenience control module so this will be in the mix as well (the function for turning the key in the drivers door to open/close all the windows).

Also I would look at the wires crossing the hinge, these were a notorious failure point in the 124s where the wires would break from constant flexing and in the worst case cause a short.