280c change over switch and vacuum element
 

in order for my defroster to turn on . theres a rod connected to a vacuum element and changeover valve . this rod needs to be pushed up fully towards vacuum bellows . is there an adjustment on rod ? or is vacuum element defective or changeover switch or both defective ? what keeps this rod fully up ???

The default setting for cars equipped with A/C is for the console fan to be active.

When the engine is running vacuum is supplied activating the diaphragm and causing the switch to trigger the defrost/heat fan which is mounted on the engine tunnel.

The A/C blower (center console) is activated by turning the A/C temperature knob. This re-routes the vacuum and allows the switch to revert to the default.