this gives you an idea about the difference between how the 2 units work
http://www.siemensvdo.com/products_s...umentation.htm
do you know what the part number is? these are from the parts database
ASW 102 SWITCH OIL PRESS, WITH OIL LIGHT $9.45
EF 9D290 A SWITCH ASSY - OIL PRESSURE, WITH OIL GUAGE $46.00