W140 S350 - Relay Location?
 

For the Electronic Switchover valve bolted to the intake?

I am not getting 12 volts to the unit in any key position. The fuse is good, so need to check the relay. Just not sure which one it is.

Thanks

It is one far back in the fuse box.You need to remove wiper relay,fuse box lid,then unscrew two bolts holding the upper cower,and remove it.Then you will see bunch of relays in there.It should be the one in the midlle in the last row.I am not 100% sure,for the position but it is one of them,I had that same problem month ago ;)

Thanks!

Well, had some time today to further diagnose. Turns out I had a bad ground in the harness going to the shutoff solenoid. I had power, but the ground was faulty, I can only assume the wiring harness issues that plagued these models was the culprit. Ran a fresh ground, and now works perfect. Thanks to all who contributed.