N75 valve

[8879gw]

Hi all , i run a diagnostics check on my mk2 galaxy and it come up with a few fault codes one of which was over boost. I started investigating why this is coming up and have founf that the n75 valve does nothing to the actuator . I have replaced the n75 an still nothing. There is vacuum going in but it doesnt allow vacuum to pas through it. My question is what triggers the n75 valve to open ?

[johnnyroper]

The engine ecu triggers it based on map sensor readings.

Have you checked the vnt actuator can move by hand? Could be sticking vanes as that's the usual cause of over boost which could cause the issue you have if map sees desired boost is achieved.

What diag equipment do you have as if got vcds can do n75 test.

[8879gw]

Hi yes the vnt actuator moves fine

[johnnyroper]

You need to get it on vcds and check the measure blocks to see what sort of reading the map is giving. If all ok then it will be a matter of belling wires out/checking for voltage from ecu.

You are 100% vac and vac hoses are all good and all the pipes are connected correctly?

[8879gw]

Hi the vac hoses are 100% i shall go into testing map with vcds an then multi meter test on the feed to it

[Chrispb]

8879gw
Are you sure the overboost fault code is current, it's normal practice to make a note of these codes then clear them then take the car for a drive and see what comes back.
You say you have no vacuum passing to the turbo actuator this scenario would give no boost (under boost) at all as the vacuum pulls the vanes to the full boost position.

Is this a new car to you? and what was the other fault codes that you said were present.