Temperature Vacuum Switch (TVS)

The bimetal disc in the switch orients itself in one of two positions, depending on its temperature. One position allows free air flow in the vacuum line; the other position blocks air flow by sealing itself against the 0-ring.

This device is mounted remotely to or directly on the air cleaner. It responds to the temperature of the inlet air heated by the exhaust manifold.

The switching temperature is below the range of normal, stabilized engine operating temperatures.

The TVS may be used to control the vacuum signal to the thermactor dump valve, reducing emissions.

The normally open TVS may block the purge vacuum signal to provide satisfactory cold driveability and reduce cold emissions. Also, the EGR may be held off to provide satisfactory cold driveability.

The normally closed TVS may allow cold spark advance to provide satisfactory driveaway.