What is a Thermo Time Switch?

A thermo time switch is a temperature sensor device normally used to turn on a cold start injector in German cars. The cold start injector is an extra injector normally mounted in the intake manifold. The thermo time switch will allow current through it to your cold start injector for a few seconds ( 3 - 8 depending on the make and model of car ) when the engine is cold and first started. This puts extra fuel in the system and helps it start. If your thermo time switch fails you may have a hard time starting when cold or, more commonly, a difficult time starting the car when hot. The problem in the latter case is the extra injector flooding the car when trying to start it.