Two speed/ single speed domestic extractor fan ?

You're really not giving enough info here. If you want to quieten it down, a series dropper is effective. There are also several other ways:

motor, since it's got 3 leads going to it, a red, blue and a white, and as I said before the white lead is terminated with an insulated crimp connector which is not connected to anything. I suspect the manufacturers (Silavent SVC6) use an universal 2 speed motor which can be used in one speed or 2 speed mode. I'm guessing that if I connect the white and blue across the mains and disconnect the red it will run at a lower speed but I 'm loath to try it.

On the back of the installation leaflet it has the following info :-

Don

why not check it with a multimeter, and if it fits what you suspect, try running it in series with a lightbulb. At your own risk.

NT

Good idea, I'll try that when I'm a bit more awake. Cheers Don

Ok I've measured the resistance of the windings and they are as follows :-

Starting at the top draw two resistances in series vertically one above the other. Now you have 3 wires connected to the network, a red one at the top, a blue one as a centre tap, and the white one at the bottom.

DC Resistance, red to blue = 278ohms. , blue to white = 80 ohms , red to white = 358 ohms The red and blue wires disappear into a printed circuit, the white is floating and insulated. My thought is to connect a changeover single pole switch (break before make ?) as follows :- common connect to pc where the blue went. c/o1 blue, c/o2 white.

Any comments appreciated.

Don

Looks like it all fits what you suspect. Switch sounds right, but test the fan first of course.

NT