Exhaust gas recirculation valve malfunction indicator apparatus

A malfunction indicating apparatus for an engine exhaust gas recirculating (EGR) system that includes a vacuum controlled first servo connected to an (EGR) valve that is spring biased to a position blocking the flow of engine exhaust gases to the engine intake manifold and moved by vacuum above a predetermined level applied to the servo to a position permitting the flow, the apparatus including a pressure balanced second servo means operably connected to the first servo and attaining a pressure unbalance condition to actuate a malfunction indicator in response to non-movement of the (EGR) valve upon application of vacuum above the predetermined level to the first servo, a source of carburetor induction passage throttle valve controlled vacuum, the pressure balancing servo means including a hollow housing divided into first and second chambers by a piston, means connecting the source of vacuum to the first servo and to the first chamber, second means connecting the first servo to the second chamber whereby flow of vacuum to the first servo flows vacuum to both first and second chambers to provide a pressure balanced neutral position of the piston, spring means acting on opposite sides of the piston to urge the piston to the balanced neutral position, malfunction indicator means engaged by and rendered operative in response to movement of the piston in one direction to a predetermined position, and control means in the second means normally blocking vacuum to the second chamber to thereby effect movement of the piston by the vacuum in the first chamber to engage the malfunction indicator means.