Thermal Modulator (2000 Engine 1967-70)

Thermal modulator provides full vacuum advance at idle when the cooling system temperature becomes too high (approximately 220° F). The advanced timing reduces cooling requirements and increases engine speed at idle, and so extremely high temperatures in cooling system can be avoided.

Fig 1: DATSUN AIR INJECTION SYSTEM (4 CYLINDER) (6 CYLINDER SIMILAR)

Courtesy of NISSAN NORTH AMERICA, INC.