DISA valve....can somebody explain?

[lightning]

How it works and what it actually does.

And how can l test it? I removed the unit from the manifold and was presented with a rectangular plastic case, with a large flap valve on one side, with what looks like a vacuum actuator.
I appled 12 volts to the electrical connection and the valve closed, then opened when l disconnected the power.
However it would only do this twice, after that there was just a click and the valve did not move. Is the plastic case a vacuum reservoir?
Pressurized by manifold pressure? If so l guess my valve is working and my lack of power is due to some other fault.

[colb]

Yes that's how it should work when power is applied to it, it shortens the length of the intake manifold, it receives its voltage from a signal generated by the ECM when the engine is at a predetermined speed and requires the shorter intake manifold length.

Carefully check the pivot points on the flap valve they have been known to fail with age and parts get sucked into the engine which you dont want to happen. These valves will also fail and flap open and closed resulting in what can be described as a clacking noise.

Sounds strange that yours worked twice with power applied then stopped reacting, could have failed.

I had a clacking Disa, bit the bullet and replaced with a new one, they are not cheap.

See if you can find one at a breakers and try that.

[lightning]

Thanks for the reply, l looked on Youtube and apparantly the box is a vacuum reservoir as l thought, and it has a one way valve that pressurizes it from the manifold.

So if you remove it from the car and apply power to the solenoid, it will operate 2-3 times and then the stored vacuum is depleted.

So it seems my fault is elsewhere. Next step is to get the codes read, as advised on my other thread "Z3 3.0 no power" on this forum.