Removal and installation, checking of the thermal time switch (BMW 3 Series E30)

The thermal time switch limits the injection time of the starting valve depending on the engine temperature.

A defective thermal time switch makes it difficult to start the engine.

Removal

Disconnect the thermal time switch connector.

Unscrew the thermal time switch.

The switch hexagon is engraved with the on-time (in the figure: 12 seconds at a temperature of 20°C). Only thermal switches with a on-time of 8 seconds at a temperature of 35°C are installed.

Heat the thermal time switch to the appropriate temperature by placing it in a water bath.

Measure resistance at 30°C. Specified values:

• between terminal "G" and ground (housing): 25-40 Ohm;
• between terminal "W" and ground: 0 Ohm (short circuit);
• between terminals "G" and "W": 25-40 Ohm.

Measure resistance at 40°C. Specified values:

• between terminal "G" and ground (housing): 50-80 Ohm;
• between terminal "W" and ground: 100-200 Ohm;
• between terminals "G" and "W": 50-80 Ohm.

If there are any deviations from the specified values, replace the thermal time switch.

Installation

Screw in the thermal time switch.

Check the coolant level and top up if necessary.



Remove air from the cooling system.