Ford Mustang/Cougar 1964-1973 Repair Guide

Temperature Activated Vacuum (TAV) System



All 1973 models using the 250 six-cylinder engine and automatic transmission built before March 15, 1973 are equipped with a Temperature Activated Vacuum (TAV) system to control distributor spark advance. The system contains a 3-way solenoid valve, an ambient temperature switch located in the front door hinge pillar, a vacuum bleed line to the carburetor airhorn and a spark delay valve.

When the ambient temperature is above 60°F, the contacts in the temperature sensor close and complete the circuit to the 3-way solenoid. This energizes the solenoid and connects the EGR vacuum port on the carburetor to the distributor vacuum advance.