What is this pneumatic switch/valve ?
 

Car = 1986 300E , UK model.

Located in the battery compartment (right hand drive vehicle, could be different on an LHD) on the firewall is a small switch or valve type device with two pneumatic tubes attached and a plug connector with two wires.
One of the tubes goes back thru the firewall , down behind the engine into the vicinity of the trans. The wiring just runs into the main harness.

Can some1 tell me what this does please , I only have limited info on this vehicle and cannot find reference to this item. I suspect it has something to do with the cruise control system.

Thanx in advance.

I do believe it's the changeover control for the S and E setting on the auto-box.

So much on these cars is pneumatically/vacuum controlled and the gearbox is no different.

The S & W switch is electrical, and switches this valve on or off.
One way it vents to air, the other connects to the inlet vacuum.

At least that's my understanding of it. You can confirm this by getting a helper to switch over the S E switch in the car and keeping your ear by the switch.
Unless we're talking about something different
:)

On my RHD version, it's on the LH inner wing/fender screwed to the strut area.

Cheers


1994 E200 Wagon 115k miles

If it has a red vacuum hose going to the transmission, that's what it is. To confirm, unplug the wiring and see if the S/E switch still works.