Pressure Converters: The Small Solenoid That Controls Turbo and EGR Vacuum

Pressure converters — also called vacuum solenoids or N75 valves on VAG applications — are small electronic valves that modulate vacuum signals to actuators like the turbo wastegate or variable-vane mechanism, and the EGR valve. The ECU controls the converter electrically; the converter controls vacuum mechanically.

What they do

On a turbo with variable-vane geometry, the vane angle changes with engine speed and load. The ECU commands the angle via the pressure converter, which modulates the vacuum signal to a diaphragm in the turbo. On an EGR system, a similar converter controls the vacuum signal to the EGR vacuum actuator.

Failure modes

Solenoid failure (electrical) — no vacuum modulation. Symptoms: turbo over- or under-boost, limp-mode.

Internal valve failure (mechanical) — vacuum signal doesn’t match electrical command. Symptoms: erratic boost or EGR operation, fault codes.

Brand

Pierburg and Hella supply OE on most VAG applications. Bosch covers other European designs. Replacement is usually straightforward — the converter is a small black box on a vacuum/electrical harness.

Find pressure converters for your engine on the Pressure Converters collection.