Distributor Spark Thermal Vacuum Switch (DS-TVS)

When engine coolant temperature is below the calibration temperature the switch allows no vacuum flow to the distributor.

When engine coolant temperature is above the calibration temperature, the DS-TVS allows ported vacuum to the distributor.
- The ported vacuum signal is controlled by a distributor spark vacuum delay valve (DS-VDV) which maintains vacuum advance during rapid throttle openings, thereby improving engine response during cold engine operation.