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I own a 1997 golf 3 TDI, motor code AFN.

At the back of the engine, there is a vacuum actuator which looks like a N75 but isn't. It isn't connected to anything on the actuator side, but is connected to the vacuum line and the ECU.

It doesn't seem to have done much to the running, as I cannot detect a difference in power or torque.

Both turbo charge valve actuator (N75) and egr valve actuator are present and accounted for, and I can't see an anti shudder valve anywhere on the intake.

What is it for?

EDIT: Here are some photos;

Closeup view. You can see the two vacuum lines, the further one is not connected to anything.

General position. It is clipped to the bottom of the cable and vacuum line tray, just behind the coolant expansion tank.

EDIT 2: When I said "It isn't connected to anything on the actuator side", I mean literally that: there is a vacuum line coming out, but it isn't connected to anything. And I cannot see an obvious connection for it.

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I found out what it is. It controls the air recirculation flap to the cabin. Nothing to do with the engine at all.

Just above the input and output pipes to the heater core on the firewall is a little plastic nozzle. This is what this actuator is supposed to be connected to.

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This is more than likely a vacuum switch which tells the computer something when it reaches a certain amount of vacuum (could also be a pressure switch doing the same thing when the turbo reaches a certain pressure, depending on which side of the turbo the "vacuum" line is located). This would be why you are only seeing the vacuum line and connection to the PCM and nothing else.

  • Sorry I was not clear. It has a vacuum line going out from it too which is not connected at the other end, so it is just like the N75, only the N75 is on the other side of the engine bay and connected to the turbo. – Tom Macdonald Aug 28 '14 at 15:21

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