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Sensor System

Consists of two bi-metal arms located in separate air passages within the thermostatic vacuum regulator. Both bi-metals are mounted as an assembly and the free ends of the arms are connected by a push pin so that the action of one bi-metal is transmitted to the other which has a ball bleed valve directly connected to the arm. This valve acts as an air bleed in the manifold vacuum line to the control vacuum chamber of the Piloted Vacuum Actuator "PVA" (power servo) and the resulting regulated vacuum positions the pilot diaphragm in accordance with the sensor indication. Sensors operate as follows:

Fig 1: Thermostatic Vacuum Regulator & Sensor Assembly
G09310818Courtesy of GENERAL MOTORS COMPANY
  1. Ambient Air Bi-metal  - Located in inner air passage of thermostatic vacuum regulator to sense temperature of air blown through this passage from plenum blower assembly (All models except Riviera) or from evaporator blower assembly (Riviera).
  2. Breath Air Bi-metal  - Located in outer air passage in thermostatic vacuum regulator to sense temperature of in-car air which is drawn in through an opening in the regulator case by the aspirating action of the ambient air flow.