280 & 280C Models
Exhaust gas recirculation only occurs when coolant temperature is between 149°F and 212°F with oil temperature above 62°F, manifold vacuum between 0 and 5.8 in. Hg and engine speed below 3200 RPM. If any of the following conditions are met, vacuum control valve will be deactivated, by means of relay boxes, which will cut off vacuum to EGR valve: Oil temperature below 62°F will cause oil temperature switch to close. Coolant temperature below 148°F or above 212°F will cause coolant temperature switches to open. Vacuum greater than 5.8 in. Hg will cause vacuum switch to open. Engine speed greater than 3200 RPM will cause RPM switch to close.