This switch appears on top of the Coolant output hose attachment elbow. Its function is to increase vacuum to the distributor, advancing it, and helping it to idle faster when the water temp gets above a certain threshold. It is primarily used for air-conditioned cars when idling. It was not connected on my car when I bought it, but I have it replaced and reconnected now.

Owner caption January 2020 · Photo 30 of 466