BACK IN STOCK! Factory BMW temperature-time switch, sometimes also called an engine coolant switch. It was used on older, classic BMW models, specifically those with D-Jetronic fuel injection systems. 
As part of the fuel delivery system, this switch is designed to monitor coolant temperature. It provides information to the engine's control unit (DME), which then adjusts the fuel mixture based on the temperature, especially during a cold start.
The switch operates at a temperature of 35 degrees Celsius for 12 seconds (35CEL 12S), according to multiple part sellers.This is a genuine BMW part, manufactured to factory specifications.
 
Its applications include: 
BMW 2002tii: 1972–1975
BMW E9 Coupes: Models such as the 3.0 CSi
BMW 5-series (E12): 1975–1976