From Alldata:

OPERATION
The control units are located in the module box and therefore protected from dust, water, oil and other substances that could damage them. Some models are equipped with a blower motor (M2/2) that controls the temperature in the module box (Phased out during MY 1994). The blower motor is in operation:

- For 1.5 seconds after engine start if the engine speed exceeds 1200 RPM.
- If the temperature in the module box is above 60 °C (140 °F).

If the module box temperature exceeds 70 °C (158 °F), the base module will store a malfunction code.