Thanks. I have been up all night working on the car and another driver (my wife) will be using it today while I sleep a few hours. I will have a chance tonight to check it out.

I was operating under the apparently-mistaken assumption that the black sensor was the pressure switch. http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=23N0NM8ZV23N0NMD92&year=1993&make=MB&model=400-E-001&category=R&part=A%2FC+Pressure+Switch and the red sensor was a temperature switch. http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=23N0NM8ZV23N0NMD92&year=1993&make=MB&model=400-E-001&category=R&part=A%2FC+Temp.+Switch

No wonder I'm having problems.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles